KR101823748B1 - Active material, nonaqueous electrolyte battery, battery pack and assembled battery - Google Patents

Abstract

According to one embodiment, a battery active material is provided. The battery active material includes active material primary particles of a monoclinic niobium titanium composite oxide. The monoclinic niobium titanium composite oxide contains at least one kind of element selected from the group consisting of Mo, V and W. The content of at least one element selected from the group consisting of Mo, V and W in the monoclinic niobium titanium composite oxide is in the range of 0.01 atm% to 2 atm%. The aspect ratio of the active material primary particles is in the range of 1 to less than 4. The crystallite size of the active material primary particles is in the range of 5 nm or more and 90 nm or less.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an active material, a non-aqueous electrolyte battery, a battery pack,

An embodiment of the present invention relates to a battery active material, a nonaqueous electrolyte battery, and a battery pack.

Recently, as a high energy density battery, a nonaqueous electrolyte battery such as a lithium ion secondary battery has been developed. The nonaqueous electrolyte battery is expected to be used as a vehicle power source such as a hybrid car or an electric vehicle, or a power source dedicated to a large-sized shaft. In particular, for vehicle applications, non-aqueous electrolyte batteries are also required to have other properties such as rapid charge-discharge performance and long-term reliability. The nonaqueous electrolyte battery capable of rapid charge / discharge has an advantage that the charging time is greatly shortened. In addition, the non-aqueous electrolyte battery capable of rapid charge and discharge can improve the power performance in the hybrid vehicle and can efficiently recover the regenerative energy of the power.

Rapid charge / discharge is possible by electron and lithium ions moving rapidly between the positive electrode and the negative electrode. In the battery using the carbon-based negative electrode, dendrites of metallic lithium were deposited on the electrode by repeating rapid charging and discharging. The dendrite generates an internal short circuit, and as a result, there is a fear of generation of heat or ignition.

Therefore, a battery using a metal composite oxide as a negative electrode active material instead of a carbonaceous material has been developed. Particularly, a battery using titanium oxide as a negative electrode active material is capable of stable rapid charging and discharging, and has a characteristic that the lifetime is longer than that of a carbon-based negative electrode.

However, titanium oxide has a higher dislocation to metal lithium (ears) than carbonaceous material. In addition, titanium oxide has a low capacity per weight. For this reason, batteries using titanium oxide have a problem of low energy density.

For example, the electrode potential of titanium oxide is about 1.5 V on the basis of metal lithium, and is higher than that of the carbon-based negative electrode (ear). The potential of the titanium oxide is electrostatically limited because it is caused by the redox reaction between Ti ^{3 +} and Ti ^{4 +} when the lithium is electrochemically intercalated and deintercalated. In addition, there is also a fact that rapid charging / discharging of lithium ions can be stably performed at a high electrode potential of about 1.5V. Therefore, it is practically difficult to lower the electrode potential in order to improve the energy density.

On the other hand, regarding the capacity per unit weight, the theoretical capacity of the lithium-titanium composite oxide such as Li ₄ Ti ₅ O ₁₂ is about 175 mAh / g. On the other hand, the theoretical capacity of a general graphite electrode material is 372 mAh / g. Therefore, the capacitance density of the titanium oxide is remarkably low as compared with that of the carbon-based negative electrode. This is due to the fact that in the crystal structure of the titanium oxide, there are few sites storing lithium, but lithium is stabilized in the structure, so that the actual capacity is lowered.

In view of the above, a new electrode material containing Ti and Nb has been studied. Particularly, the monoclinic Nb-Ti based composite oxide represented by TiNb ₂ O ₇ compensates Ti for tetravalent to trivalent ions when Li is inserted and Nb for trivalent states at 5-valence. As a result, the monoclinic Nb-Ti based composite oxide represented by TiNb ₂ O ₇ has attracted attention because its theoretical capacity becomes 387 mAh / g at a high capacity.

An object of the present invention is to provide a battery active material capable of realizing a nonaqueous electrolyte battery excellent in input / output characteristics and cycle characteristics, a nonaqueous electrolyte battery including the battery active material, and a battery pack including the nonaqueous electrolyte battery.

According to the first embodiment, an active material is provided. The battery active material includes active material particles of a monoclinic niobium titanium composite oxide. The monoclinic niobium titanium composite oxide contains at least one kind of element selected from the group consisting of Mo, V and W. The content of at least one element selected from the group consisting of Mo, V and W in the monoclinic niobium titanium composite oxide is in the range of 0.01 atm% to 2 atm%. In the active material particle, the aspect ratio of the primary particles is in the range of 1 to less than 4. The crystallite size of the active material particles is in the range of 5 nm or more and 90 nm or less.

According to the second embodiment, a nonaqueous electrolyte battery is provided. The nonaqueous electrolyte battery includes a negative electrode, a positive electrode, and a nonaqueous electrolyte. The negative electrode includes the battery active material according to the first embodiment.

According to the third embodiment, there is provided a battery pack comprising the nonaqueous electrolyte battery according to the second embodiment.

According to one embodiment, it is possible to provide a battery active material capable of realizing a non-aqueous electrolyte cell excellent in input / output characteristics and cycle characteristics.

1 is a schematic diagram showing the crystal structure of monoclinic TiNb ₂ O ₇ .
Fig. 2 is a schematic view showing the crystal structure of Fig. 1 viewed from another direction.
3 is a sectional view of an example flat non-aqueous electrolyte cell according to the second embodiment.
4 is an enlarged sectional view of part A of Fig.
5 is a partially cutaway perspective view schematically showing another flat non-aqueous electrolyte cell according to the second embodiment.
6 is an enlarged cross-sectional view of part B in Fig.
7 is an exploded perspective view of an example battery pack according to the third embodiment.
8 is a block diagram showing an electric circuit of the battery pack of Fig.
9 is a spectrum obtained by wide angle X-ray diffraction measurement of the active material of Example 1. Fig.
10 is a typical SEM image of the active material of Example 1. Fig.
11 is a spectrum obtained by wide angle X-ray diffraction measurement on the active material of Comparative Example 1. Fig.
12 is a typical SEM image of the active material of Comparative Example 1. Fig.
13 is a schematic perspective view of an electrode group included in the test battery of Example 1. Fig.

Hereinafter, embodiments will be described with reference to the drawings. Throughout the embodiments, the same reference numerals are given to common components, and redundant description is omitted. It is to be noted that the drawings are schematic diagrams for explaining the embodiments and promoting their understanding, and the shapes, dimensions, and ratios thereof are different from actual apparatuses, Design can be changed.

(First Embodiment)

According to the first embodiment, a battery active material is provided. The battery active material includes active material particles of a monoclinic niobium titanium composite oxide. The monoclinic niobium titanium composite oxide contains at least one kind of element selected from the group consisting of Mo, V and W. The content of at least one element selected from the group consisting of Mo, V and W in the monoclinic niobium titanium composite oxide is in the range of 0.01 atm% to 2 atm%. In the active material particle, the aspect ratio of the primary particles is in the range of 1 to less than 4. The crystallite size of the active material particles is in the range of 5 nm or more and 90 nm or less.

The niobium titanium composite oxide is a composite oxide containing a niobium element and a titanium element having a crystal structure called a Wadthley-Roth phase. In this composite oxide, the octahedron formed by the metal ion composed of the Nb element and the Ti element and the oxygen ion form a block sharing the apex. Further, in the crystal structure of the niobium titanium composite oxide, a tetrahedral structure formed by a parasitic structure or a metal ion composed of Nb element and Ti element and oxygen ions is sandwiched and connected between the blocks, Direction.

Niobium-titanium composite oxide includes, for example, _{TiNb 2 O 7, Ti 2 Nb} 10 O 29, TiNb 14 O 37, TiNb exists a plurality of different, such as ₂₄ O _62. Which phase of the niobium-titanium composite oxide to take is determined by the molar ratio of Nb / Ti in the complex oxide.

More preferably, it is any Nb / Ti = 2 the TiNb ₂ O composite oxide containing ₇ different. In the complex oxide TiNb ₂ O ₇ , the crystal structure is attributed to the monoclinic space group C2 / m. In this crystal structure, the octahedron formed by the metal ions composed of the Nb element and the Ti element and the oxygen ion form blocks with 3 vertically and 3 horizontally while sharing apexes. Further, in this crystal structure, layers in which blocks are connected by side sharing have a structure in which they are stacked in the b-axis direction. The composite oxide TiNb ₂ O ₇ is characterized in that the capacity of the active material, which is a capacity capable of absorbing lithium ions, is the highest because the composite oxide TiNb ₂ O ₇ has the widest space among the niobium titanium composite oxides.

On the other hand, the composite oxide to be synthesized in addition to Nb / Ti = 2 is likely to be in a mixed state including two or more phases of TiNb ₂ O ₇ , Ti ₂ Nb ₁₀ O ₂₉ , TiNb ₁₄ O ₃₇ and TiNb ₂₄ O ₆₂ have. The phase of TiNb ₂ O ₇ , Ti ₂ Nb ₁₀ O ₂₉ , TiNb ₁₄ O ₃₇ and TiNb ₂₄ O ₆₂ is characterized in that the capacity is small and the rate characteristic is large as compared with the phase of TiNb ₂ O ₇ . For this reason, the niobium titanium composite oxide including this mixed phase can realize an improved rate characteristic. The composite oxide having 1? Nb / Ti? ₂ can be obtained, for example, as a mixed phase of rutile type TiO ₂ and TiNb ₂ O ₇ . When the rutile type TiO ₂ phase occludes Li, a part of the occluded Li may remain on the rutile type TiO ₂ even if the active material is completely discharged, for example. This residual Li can increase the electrical conductivity of the rutile type TiO ₂ phase, and furthermore, the entire active material. Therefore, the active material containing the rutile type TiO ₂ and TiNb ₂ O ₇ mixed with each other can realize a non-aqueous electrolyte cell capable of exhibiting excellent rate characteristics.

The ratio of Ti / Nb is determined according to the design and use of the battery, but from the viewpoint of not sacrificing the active material capacity, the ratio of Ti / Nb is preferably 1.5 Nb / Ti <5.

Then, in more detail described with reference to the accompanying drawings of one example of TiNb ₂ O ₇ of the fixed form monoclinic niobium titanium composite oxide.

1 is a schematic diagram showing a crystal structure of monoclinic shaping TiNb ₂ O _7. Fig. 2 is a schematic diagram showing the crystal structure of Fig. 1 viewed from another direction.

1, the crystal structure of the monoclinic shaping TiNb ₂ O _7, and the metal ions 101 and the oxide ion (102) constitutes a part of the skeleton 103. The Nb ions and Ti ions are randomly arranged in the metal ion 101 in a ratio of Nb: Ti = 2: 1. As shown in Fig. 1, the space portion 104 is present between the skeleton structure portions 103 by arranging the skeleton structure portions 103 three-dimensionally alternately. This void portion 104 becomes a host of lithium ions. This void portion 104 can occupy a major portion of the entire crystal structure, as shown in Fig. In addition, the void portion 104 can stably maintain the structure even when lithium ions are inserted.

When lithium ions are inserted into the void portion 104, the metal ions 101 constituting the skeleton structure portion 103 are reduced in triplicate, thereby maintaining the electrical neutrality of the crystal. In the monoclinic niobium titanium composite oxide TiNb ₂ O ₇ , Ti ions are reduced not only in tetravalency but also in trivalence, and Nb ions are reduced in trivalent to pentavalent. Therefore, the monoclinic complex oxide TiNb ₂ O ₇ has a larger reduction number per active material mass than a compound containing only tetravalent cation Ti ions. As a result, the monoclinic complex oxide TiNb ₂ O ₇ can maintain electrical neutrality of crystals even when more lithium ions are inserted. Since it is possible to insert more lithium ions in this manner, the monoclinic complex oxide TiNb ₂ O ₇ can increase the energy density as compared with a compound such as titanium oxide containing only tetravalent cations.

In addition, the monoclinic complex oxide TiNb ₂ O ₇ having the crystal structure shown in Figs. 1 and 2 has a plurality of regions having two-dimensional channels with fast diffusion of lithium and a lithium path connecting these regions. More specifically, in FIG. 1, the region 105 and the region 106 are portions having two-dimensional channels in the [100] direction and the [010] direction, respectively. Respectively, as shown in Figure 2, the crystal structure of the monoclinic shaped composite oxide TiNb ₂ O _7, the gap portion 107 with a [001] orientation exist. This void portion 107 has a tunnel structure favorable to the conduction of lithium ions and becomes a lithium path in the [001] direction connecting the region 105 and the region 106. [ The existence of the lithium path 107 makes it possible for the lithium ion to pass through the region 105 and the region 106. [

Thus, in the crystal structure of the monoclinic complex oxide TiNb ₂ O ₇ , the equivalent insertion space of lithium ions is large and structurally stable. In addition, the monoclinic complex oxide TiNb ₂ O ₇ can increase energy density as compared with a compound not containing a pentavalent cation. In the crystal structure of the monoclinic complex oxide TiNb ₂ O ₇ , regions 105 and 106 having two-dimensional channels with fast diffusion of lithium ions and a lithium path 107 in the [001] direction connecting them are present Therefore, the monoclinic shaped composite oxide can improve the insertion performance of lithium ions into the insertion space and the desorption of lithium ions from the insertion space, and at the same time, the space contributing to the insertion and desorption of lithium ions can be effectively . As a result, the monoclinic composite oxide TiNb ₂ O ₇ is capable of providing a high capacity. Specifically, the theoretical capacity of the monoclinic complex oxide TiNb ₂ O ₇ is about 387 mAh / g, which is twice or more the value of the titanium oxide having the spinel structure.

The monoclinic niobium titanium composite oxide may have a structure similar to the crystal structure shown in Figs. 1 and 2 even if the composition is different. Therefore, the monoclinic niobium titanium composite oxide can provide a high capacity.

The monoclinic niobium titanium composite oxide has a lithium intercalation potential of about 1.5 V (vs. Li / Li ⁺ ). Therefore, by using such a composite oxide as an active material, it is possible to provide a battery capable of stable repeated charge / discharge.

From the above, it is possible to provide a battery active material having an excellent rapid charge-discharge performance and a high energy density by using an active material containing a monoclinic niobium titanium composite oxide.

In order to obtain such a monoclinic niobium titanium composite oxide as an active material having sufficient crystallinity, it was necessary to perform firing at a high temperature of 1100 DEG C or higher for a long time. However, such high-temperature firing for a long time has a problem in that the productivity is low.

In order to solve this problem, there is a policy of including as the sintering aid a compound containing at least one element selected from the group consisting of Mo, V and W in the precursor provided for firing.

In general, a compound containing at least one element selected from the group consisting of Mo, V and W is known to have a low melting point. When such a compound having a low melting point is included in a raw material and is baked, the compound reaches a melting point at the time of baking, thereby becoming a liquid phase. This liquid phase can improve the adhesion between the particles. As a result, by using such a compound as a sintering aid, sintering at a low temperature becomes possible.

Further, in the niobium titanium composite oxide, elements such as Mo, V, and W can replace some of the elements of Nb and / or Ti. Therefore, these elements can prevent occurrence of an abnormality including these remaining elements in the niobium titanium composite oxide. Accordingly, the active material containing the niobium titanium composite oxide containing at least one element selected from the group consisting of Mo, V, and W can be used as a positive electrode active material because of the stress caused by the volume expansion or contraction during Li occlusion and discharge. It is possible to suppress occurrence of cracking. Therefore, the nonaqueous electrolyte battery including the active material particles containing the niobium titanium composite oxide containing at least one element selected from the group consisting of Mo, V and W can be stably charged and discharged.

On the other hand, in the conventional method, the sintering temperature can be lowered by adding a compound containing at least one element selected from the group consisting of Mo, V and W and functioning as a sintering aid. However, The cycle characteristics tend to be lower than those of the active material obtained without using such a sintering aid.

As a result of intensive studies, the inventors of the present invention have found that this phenomenon is caused by what is described below.

First, when a compound containing at least one element selected from the group consisting of Mo, V and W is added as a sintering aid and baking is performed for a long time, crystal growth proceeds in the direction of one short axis in the niobium titanium composite oxide Throw away. The niobium-titanium composite oxide in which crystals are anisotropically grown thus contains coarse crystals in the form of scales or needles. As a result, the thus obtained niobium titanium composite oxide becomes composite oxide particles having a long axis / short axis ratio, that is, a large aspect ratio. In particular, such uniaxial growth tends to occur in the direction of [010] most significant to the diffusion of Li. For this reason, the increase in the aspect ratio accompanied by uniaxial growth of the complex oxide particle is directly related to the increase in the diffusion length in the Li solid.

On the other hand, in the niobium titanium composite oxide, as the storage amount of Li increases, the diffusion rate of Li ions in the solid decreases. Therefore, in the nonaqueous electrolyte battery fabricated by incorporating the niobium titanium composite oxide into the electrode, in which the in-solid diffusion length is increased by the uniaxial growth as described above, an overvoltage is generated at the time of charging and an electrochemical load . Further, if the in-solid diffusion length is long, the amount of Li absorbed and the amount of released Li decrease. Therefore, the nonaqueous electrolyte battery produced by incorporating the niobium titanium composite oxide having a long in-solid diffusion length into the electrode exhibits a poor rate characteristic. In addition, the nonaqueous electrolyte battery fabricated by incorporating a niobium titanium composite oxide having a long solid diffusion length into the electrode increases the overvoltage on the reduction side due to an increase in the overvoltage to the negative electrode, thereby lowering the cycle characteristics.

Based on the above findings, the present inventors have conducted intensive studies and have realized the battery active material according to the first embodiment.

Concretely, regarding the active material particles contained in the battery active material according to the first embodiment, the aspect ratio of the primary particles of the active material particles is in the range of 1 to less than 4. The crystallite size of the active material primary particles is in the range of 5 nm or more and 90 nm or less.

The aspect ratio of the active material primary particles and the active material of the niobium titanium composite oxide in which the crystallites of the primary particles are within the above range include at least one kind of element selected from the group consisting of Mo, V and W, An increase in the diffusion length in the Li solid in the active material particle at the time of growth is suppressed. The battery active material containing such active material particles can suppress overvoltage at the time of charging and side reactions at the reduction side when used in a nonaqueous electrolyte battery. As a result, the battery active material according to the first embodiment can realize a nonaqueous electrolyte battery excellent in input / output characteristics and cycle characteristics.

On the other hand, in the active material particles having an aspect ratio of primary particles of 4 or more, the diffusion distance in Li solids is too long. Therefore, as described above, the nonaqueous electrolyte battery incorporating such a battery active material containing the active material particles of the niobium titanium composite oxide has a low charge-discharge capacity due to the generation of an overvoltage, a decrease in the amount of Li adsorption and discharge and a decrease in side- The characteristics and the cycle are degraded. In addition, the aspect ratio is the major axis / minor axis ratio, and since the major axis does not become shorter than the minor axis, the aspect ratio is not less than 1. A preferable range of the aspect ratio is 1 or more and 3 or less.

In addition, the active material particles having a crystallite size of less than 5 nm in the active material particles are too small in crystallite size. In such active material particles, the Li insertion site becomes unstable due to the influence of the active material interface. As a result, the crystal structure at the occlusion and release of Li is not stable and the cycle characteristics are lowered with an increase in side reaction. On the other hand, in the active material particles having a crystallite size of 90 nm or more, the diffusion distance in the Li solid is too long. Therefore, as described above, the nonaqueous electrolyte battery incorporating such a battery active material containing the active material particles of the niobium titanium composite oxide has a low charge-discharge capacity due to the generation of an overvoltage, a decrease in the amount of Li adsorption and discharge and a decrease in side- The characteristics and the cycle are degraded. A preferable range of the crystallite size is 10 nm or more and 70 nm or less.

In the battery active material according to the first embodiment, the content of at least one element selected from the group consisting of Mo, V and W in the monoclinic niobium titanium composite oxide is 0.01 atm% to 2 atm%. The battery active material having a content of at least one element selected from the group consisting of Mo, V and W in the monoclinic niobium titanium composite oxide is less than 0.01 atm%. When the addition amount of these elements serving as a sintering aid at the time of firing is low . Therefore, unless such a battery active material is provided for firing at a high temperature for a long time, the crystal of the niobium titanium composite oxide is not sufficiently densified and an image having sufficient crystallinity can not be obtained, so that it is difficult to exhibit a sufficient capacity Do. When the content of the element is larger than 2 atm%, the content of these elements exceeds the solubility limit of these elements in the niobium-titanium composite oxide, so that a large amount of the element remains in the active material particles. In the battery active material containing the above-mentioned active material particles, there is a fear that the active material is broken due to the volume expansion and shrinkage accompanying shrinkage during storage and discharge of Li, and the cycle characteristics are lowered.

The content of at least one element selected from the group consisting of Mo, V and W in the monoclinic niobium titanium composite oxide is preferably 0.01 atm% to 0.3 atm%.

The monoclinic niobium titanium composite oxide may contain one kind of element selected from the group consisting of Mo, V and W, two kinds of elements selected from the group consisting of Mo, V and W, or Mo , V, and W may be included.

The monoclinic niobium titanium composite oxide contained in the active material for a battery according to the first embodiment is selected from the group consisting of O elements (oxygen elements, hereinafter the same), Ti elements, Nb elements, and Mo, V and W May include another element other than at least one kind of element. Examples of other elements include Ta, Fe, Bi, Sb, As, P, Cr, B, Na, Mg, Al and Si. One kind of element may be used as another element, or a plurality of kinds of elements may be used as another element. These other elements can be expected to improve properties by substituting a part of the Ti element of the compound TiNb ₂ O ₇ and / or a part of the Nb element.

Accordingly, the niobium-titanium composite oxide is contained in the battery active material according to the first embodiment, the formula _{Ti 1 -a- c M1 a M3 c} Nb 2 -bd M2 b M4 d O 7 (0≤a <1, 0 B < 1, 0 < c + d < 1). M1 and M3 in the formulas, means a substituted element with a portion of the element Ti in the composition formula TiNb ₂ O _7. The M2 and M4 in the formula of the niobium-titanium composite oxide contained in the battery active material according to the first embodiment, refers to the substitution element with a portion of Nb element in the composition formula TiNb ₂ O _7. The element M1 and the element M2 are at least one selected from the group consisting of Nb, Ta, Fe, Ti, Bi, Sb, As, P, Cr, B, The element M1 and the element M2 may be the same or different from each other. The element M3 and the element M4 are at least one selected from V, Mo and W. The elements M3 and M4 may be the same or different from each other.

The niobium titanium composite oxide included in the battery active material according to the first embodiment is obtained by partially replacing the Ti element in the compound TiNb ₂ O ₇ with the element M 1 or the element M 3 and / or partially replacing the Nb element with the element M 2 or the element M 4 It can be expected that the cell characteristics can be further improved by substitution. For example, when V, Ta, Bi, Sb, As, and P are used as the substitutional elements, some of the Nb element and the Ti element may be substituted. Since these elements are pentavalent, the electron conductivity of the compound TiNb ₂ O ₇ can be improved by substituting a part of the Ti element. Thus, it is expected that capacity and rapid charging performance can be further improved. The hexavalent elements such as Cr, Mo, and W may partially replace the Ti element and the Nb element. As a result, the improvement of the electron conductivity of the compound TiNb ₂ O ₇ can be expected. Further, since the element such as B, Na, Mg, or Si is a light element rather than the Ti element, it is expected that the capacity can be further improved by substituting a part of Ti with these elements. The trivalent element such as Fe and Al may substitute a part of the Ti element. As a result, the improvement of the electron conductivity of the compound TiNb ₂ O ₇ can be expected.

Equivalent characteristics can be obtained by substituting a part of the Nb element with Ta in the compound TiNb ₂ O ₇ . This is because Ta is a material contained in a column byte which is an ore containing Nb, and Nb and Ta have similar physical, chemical and electrical properties.

During the production of the composite oxide, oxygen deficiency may occur in the raw material or the intermediate product. Incidentally, inevitable impurities contained in the raw materials and impurities incorporated during the production are also present in the produced composite oxides. Accordingly, the niobium-titanium composite oxide is, for example, the inevitable by a factor, the formula _{Ti 1 -ac M1 a M3 c Nb} 2-bd M2 b M4 d O 7 (0≤a <1, 0≤b < 1, 0 < c + d < 1). For example, by oxygen deficiency occurring in the production of oxide by causing the formula _{Ti 1 -a- c M1 a M3 c} Nb 2 -b- d M2 b M4 d O 7 -δ (0≤a <1, 0 An oxide having a composition expressed by? B <1, 0 <c + d <1,? <0.3) may be produced.

The particles of the monoclinic niobium titanium composite oxide included in the battery active material according to the first embodiment may include at least one of primary particles and secondary particles in which primary particles are aggregated. The primary particles may be complexed with carbon, for example, in a state in which a carbon-containing layer is coated on a part of the surface. The secondary particles may be aggregated primary particles that are complexed with carbon. Alternatively, the secondary particles may be secondary particles formed by agglomerating primary particles, and may be combined with carbon in a state where a part of the surface of the secondary particles is covered with a carbon-containing layer.

The battery active material according to the first embodiment preferably has an average primary particle diameter of between 0.01 탆 and 5 탆, more preferably between 0.1 탆 and 3 탆. The battery active material according to the first embodiment preferably has an average secondary particle diameter of between 1 탆 and 100 탆, more preferably between 5 탆 and 30 탆.

The battery active material according to the first embodiment can be produced, for example, by a production method using the liquid phase synthesis method described below.

In the liquid phase synthesis method, since the reaction proceeds in a state where the Nb element and the Ti element are mixed at the atomic level, it is possible to obtain a monoclinic niobium titanium composite oxide with a short firing time. Further, in the production method of this example, rapid heating is carried out at a temperature of 600 ° C to 900 ° C or less and at a heating rate of 20 ° C / minute or more upon firing. In such a manufacturing method, a small active material which can suppress anisotropy and particle growth of crystals and whose crystallite size is in the range of 5 nm or more and 90 nm or less and whose aspect ratio of primary particles is in the range of 1 to less than 4 . This production method is specifically as follows. In addition, in the following explanation of the manufacturing method, at least one kind of element selected from the group consisting of Mo, V and W is referred to as an additive element.

First, a mixed solution is prepared by mixing an acidic solution (A) in which a Ti compound is dissolved, an acidic solution (B) in which an Nb compound is dissolved, and an acidic solution (C) containing an additive element. The starting material of each acidic solution is not particularly limited. For example, a solution obtained by dissolving a hydroxide, a sulfide, an oxide, a salt, an alkoxide or an organic substance in a suitable solvent such as pure water, ethanol or acid may be used. The molar ratio of each element in the mixed solution is a molar ratio at the time of charging, and may be different from the composition ratio of each element in the active material after production.

Subsequently, the coprecipitate precipitates are precipitated by mixing the alkali solution as the pH adjusting agent into the mixed solution prepared as described above. The pH adjuster is preferably an alkali solution, preferably pH 8 or more, and more preferably pH 12 or more. it is preferable because a solution having a large pH can deposit coprecipitate precipitates with a small liquid amount. As the pH adjusting agent, for example, ammonia water may be used. As a mixing method, a method of dropping a pH adjusting agent into the mixed solution, or a method of dropping a mixed solution in the pH adjusting agent may be used. By controlling the method of dropping the liquid, the speed, the timing, and the temperature of the solution, the degree of aggregation of the precipitates and the shape of the particles can be controlled. It is more preferable that the solution temperature is lower than the room temperature and that the pH adjusting agent is gradually added to the mixed solution gradually in order to suppress excessive aggregation. The pH of the mixed solution containing Ti and Nb is adjusted to the alkali side by adding a pH adjusting agent. The pH can be adjusted while monitoring the precipitation condition of the coprecipitated precipitate. The pH is set in the range of 1 to 10, preferably 6 to 9, as a standard. Thus, coprecipitated precipitates containing Ti, Nb and the additive elements can be precipitated.

In addition, finer particles can be obtained by conducting a closed heat treatment with an autoclave vessel before and after the step of adjusting the pH. The heat treatment temperature in the autoclave vessel is preferably 160 ° C or more and 200 ° C or less, and the sintering time is preferably 5 hours or more.

Subsequently, the precipitated coprecipitate precipitate is washed. As the solution for cleaning, for example, pure water is preferably used. As a criterion for washing, the washing is sufficiently carried out until the pH of the waste solution is in the range of 6 to 8, more preferably close to neutrality. After sufficiently washing, filtration and drying are performed to obtain a precursor powder.

The precursor thus obtained is a precipitate in which Nb and Ti and the additional elements are homogeneously mixed, and more preferably a complex hydroxide of amorphous. By making the amorphous precursor powder in which Ti and Nb and the additional elements are homogeneously mixed, the reactivity at the time of firing can be increased. Thereby, by providing such amorphous precursor powder to the calcination, the monoclinic niobium titanium composite oxide can be obtained by baking at a lower temperature and in a shorter time than the solid phase reaction method and the like. That is, in the method of this example, the temperature and time in the firing step can be suppressed.

Precursor powder after filtration and drying may be aggregated. In addition, the particle size of the primary particles may be uneven due to the influence of the kind of the raw material. In this case, it is preferable to pulverize by a mechanical milling method such as a ball mill or a bead mill.

Then, the obtained precursor powder is calcined. The firing is carried out at a temperature in the range of 600 캜 to 900 캜. More preferably, the temperature is in the range of 700 to 800 ° C. The firing time is 1 minute to 1 hour. More preferably, the baking time is 30 minutes to 1 hour. By firing under these conditions, it is possible to form an image composed of a single crystalline niobium titanium composite oxide having high crystallinity.

Further, the rate of temperature rise in this firing is set to 20 DEG C / min or more. By increasing the temperature raising rate in this manner, the holding time at high temperature becomes shorter, so that anisotropic growth of crystals can be suppressed, and it is possible to obtain particles having a smaller aspect ratio of primary particles.

From the viewpoint of improving the crystallinity while suppressing grain growth and intergranular necking, the annealing step for 1 minute to 1 hour at a temperature in the range of 600 占 폚 to 700 占 폚 and at a temperature lower than the first baking is carried out It can be added before or after. In this annealing step, the temperature raising rate is 20 ° C / min or more.

The firing atmosphere may be any of inert gas atmosphere such as air, nitrogen, argon, helium, or vacuum atmosphere, but an oxidizing atmosphere is preferable for obtaining an oxide, and more specifically, an atmosphere is preferable. Alternatively, the oxygen concentration may be sintered in an atmosphere of which the concentration is intentionally increased.

The powder after firing may be either necking the particles or excessively growing the particles. Therefore, pulverization by a mechanical milling method such as a ball mill or a bead mill is preferable because fine particles can be formed further. However, if mechanical pulverization is carried out, the crystallinity of the active material may be damaged. In this case, it is preferable to perform annealing for 1 minute to 1 hour at a temperature within the range of 600 占 폚 to 800 占 폚, which can be improved by adding this milling step. In this annealing step, the anisotropic growth of the crystal can be suppressed by raising the heating rate to 20 DEG C / min or more.

Further, carbon may be further complexed to the fired powder. The method of combining with carbon is not particularly limited. Examples of the carbon source include saccharides, polyolefins, nitriles, alcohols, and organic compounds including benzene rings. It is also possible to carry carbon black, graphite or the like on the fired powder by a mechanical method such as a planetary ball mill. The compounding can be performed, for example, by mixing the calcined powder with a carbon source and then firing in a reducing atmosphere. The firing is preferably carried out at a temperature of 900 DEG C or lower. If the sintering temperature is higher than 900 DEG C, the reduction reaction of the Nb element proceeds and there is a risk of abnormal precipitation. As the reducing atmosphere, an atmosphere such as nitrogen, carbon dioxide, or argon is preferable.

When the particle size after firing is 1 占 퐉 or less, it is preferable to assemble by a method such as spray drying because the dispersibility of the slurry in the electrode manufacturing step is improved and the liquidity is stabilized.

Next, a method of determining the composition ratio of the elements contained in the battery active material, a method of calculating the aspect ratio of the primary particles of the active material particles, and a method of calculating the crystallite size will be described.

The active material powder can be prepared for each measurement after adjustment by a generally known pretreatment method.

On the other hand, when the measurement is performed on the battery active material contained in the battery, the battery active material is taken out from the battery as follows.

First, lithium ions are completely desorbed from the niobium titanium composite oxide in order to grasp the crystal state of the active material particles contained in the active material for a battery. For example, when the measurement is performed on the active material particles contained in the negative electrode, the battery is completely discharged. However, there is a case where lithium ions are remained in a small amount even in the discharge state.

Subsequently, the battery is decomposed in a glove box filled with argon, and an electrode containing the active material to be measured is taken out. Subsequently, the taken out electrode is washed with an appropriate solvent. When the battery is a nonaqueous electrolyte battery, it is preferable to use a nonaqueous solvent of a nonaqueous electrolyte, for example, ethylmethyl carbonate or the like.

Then, a layer (for example, a negative electrode layer to be described later) containing the active material to be measured is peeled off from the washed negative electrode. For example, a layer containing an active material can be peeled off by irradiating an ultrasonic wave to an electrode substrate in a solvent.

Subsequently, the layer containing the active material is heated in the air for a short time. This heating is carried out, for example, at 500 DEG C over 1 hour. By this heating, other components such as a binder and a conductive agent are removed. On the other hand, the molar ratio of the elements constituting the active material does not change even after heating. The residue after heating is dissolved in an acid to prepare a measurement sample. This measurement sample is provided for each composition analysis. Further, in the SEM measurement, observation is carried out without being dissolved in an acid, while remaining in powder.

<Method of Determining Composition Ratio>

The composition of the battery active material and the content of the elements contained in the active material can be identified by inductively coupled plasma (ICP) emission spectroscopy and inert gas fusion-infrared absorption.

Concretely, first, the active material to be measured is dissolved by alkali dissolution or acid decomposition to prepare a measurement sample. In the case of analyzing the active material contained in the battery, the phase containing the active material is heated as described above, and the remaining residue is dissolved in the acid to prepare a measurement sample. In manufacturing, the amount (concentration) of the active material in the sample to be measured is determined.

The measurement sample thus prepared is analyzed by ICP emission spectroscopy to determine the concentration of each metal element per unit weight in the measurement sample. From this measurement result, the composition ratio of the metal element contained in the active material can be calculated.

Further, the content of the O element contained in the active material can be calculated by the inert gas melting-infrared absorption method, and the concentration per unit weight of the active material can be calculated.

From the results obtained by the above method, it is possible to calculate the amount of the at least one element of the Ti element, the Nb element, the Mo element, the W element or the V element, the substitution element and the O element per unit weight with respect to the active material. From these amounts of materials, it is possible to calculate the composition ratio (molar ratio) with respect to each element in the active material.

The content of at least one element selected from the group consisting of Mo, W and V in the niobium titanium composite oxide is preferably at least one element selected from the group consisting of Mo, W, or V of the element per unit weight of the active material (Unit: atm%) of the molar ratio by subtracting the amount of the substance of Ti, Nb, Mo, W, or V from the total amount of the elements of O,

Further, when the active material to be measured contains a phase-in-phase of the niobium-titanium composite oxide and other phases, there is a problem that the ratio of the above-mentioned molar ratio can not be strictly measured. When the active material includes a plurality of phases, the composition ratio of the phase of the niobium titanium composite oxide can be determined, for example, as follows.

First, the active material is provided for wide-angle X-ray scattering measurement. Wide angle X-ray scattering measurement will be described later. The wide-angle X-ray scattering measurement performed here is performed under the condition that a result that can perform the Rietveld analysis can be obtained. The results obtained by this wide angle X-ray scattering measurement are provided for Rietveld analysis. From this result, the composition ratio of each phase contained in the active material is separated.

On the other hand, when the active material is subjected to analysis such as EDX analysis, the composition of at least one of Ti element, Nb element, Mo, W, or V contained in the phase other than the niobium titanium composite oxide, Determine the element. Thereby, the amount of each constituent element per unit weight of the phase other than the niobium titanium composite oxide can be calculated.

First, by measuring the amount of each constituent element contained per unit weight, with respect to the phase other than the niobium titanium composite oxide, from the amount of each element contained in the active material having the unit weight determined as described above, the amount of the niobium titanium composite oxide contained in the active material , The amount of each constituent element per unit weight can be calculated. From this result, the content of at least one element of Mo, W or V in the niobium-titanium composite oxide can be determined.

&Lt; Calculation method of aspect ratio of primary particles of active material particles >

The aspect ratio of the primary particles of the active material particles is measured in the following order. First, the ratio of the particle diameter A to the particle diameter A in the direction in which the largest particle diameter of the primary particles is short, that is, the particle diameter of the short axis is A and the particle diameter of the long axis is B, B / A. It is preferable that the active material particles contained in the battery active material according to the first embodiment do not contain a large number of particles having an aspect ratio of 1 or more and less than 4 and an aspect ratio of 4 or more.

The aspect ratio of the primary particles is selected from SEM images by one primary particle having the highest aspect ratio contained therein. The particles of aggregated particles joined by necking are regarded as independent primary particles. Next, it is defined by calculating the ratio B / A by setting the particle diameter in the direction in which the particle diameter is the shortest to be A and the particle diameter in the direction where the particle diameter is the longest to be the largest. The same operation is calculated from 30 randomly selected images, and the average value is defined as the aspect ratio of the primary particles of the active material particles. The measurement conditions of the SEM are, for example, conditions described in the examples.

&Lt; Calculation method of crystallite size of active material particles >

The crystallite size of the active material particle can be determined by determining the half width of the peak from the X-ray diffraction pattern obtained by the wide-angle X-ray diffraction method on the active material particle and using the Scherr's formula shown below .

The half width of the peak uses a value obtained by fitting the spectrum. The fitting of the spectrum is performed as follows. First, removal of the background, separation of K alpha 1 peak and K alpha 2 peak, and pretreatment by smoothing are performed. Subsequently, a peak search by a second order differentiation method is performed on the spectrum after the pre-treatment. Subsequently, the peak profile formed by the peak selected by the peak search is subtracted from the spectrum after the preprocess, thereby obtaining the background profile. The background profile thus obtained is fitted by a polynomial. By using the peak profile formed by the peak selected by the peak search and the information of the background, the profile fitting by the least squares method is performed in the spectrum after the preprocessing to optimize the respective parameters of the peak information and the background information. Also, the fitting function of the peak uses a partitioned pseudo Voigt function. This method can automatically perform a series of operations, for example, by performing automatic profile processing using analysis software "Rigaku PDXL2 ver.2.1". By this method, the half width of each peak can be obtained.

[Equation 1]

Here, K is the Scherrer constant,? Is the wavelength of the Cu-K? Line (= 0.15406 nm),? _E is the half width of the diffraction peak, and? _O is the correction width of the half width.

Diffraction peaks used for calculation, the space group C2 / m, which corresponds to 110 single yarn shaping niobium-titanium composite oxide TiNb ₂ O ₇ crystal structure surfaces belonging to, 2θ = 23.9317 ° ± 0.2 ° peak la obtained in the range of . The Scherrer constant is K = 0.94. The half value width correction value under the above condition is set to Y = 0. However, when the measurement system is different, it can be considered that the half width is different. In this case, an accurate value can be obtained by calculating the correction value using a standard sample.

Next, a wide-angle X-ray diffraction measurement relating to a battery active material, which is performed to determine the crystallite size of the active material particles, will be described.

First, the active material particles contained in the sample provided for the measurement are crushed until aggregation is sufficiently released. As a standard, it is preferable that the average particle diameter be 20 mu m or less. The average particle diameter can be obtained by a laser diffraction particle size distribution measuring apparatus.

Then, the crushed sample is filled in the holder portion of the glass sample plate having the holder portion. As a sample, for example, a glass sample plate having a holder portion with a depth of 0.2 mm can be used. After the sample is filled in the holder portion, the sample is sufficiently pressurized using a glass plate, and the surface is smoothed. The glass sample plate thus filled with the sample is placed in powder X-ray diffraction, and measurement is carried out by the X-ray diffraction method using a Cu-K? Line.

The measuring apparatus and measuring conditions are, for example, carried out in the following manner.

X-ray Diffraction Apparatus: SmartLab manufactured by Rigaku Kabushiki Kaisha

X-ray source: CuK alpha ray

Output: 40kV, 200mA

Package measurement name: Universal measurement (concentration method)

In-line parallel slit opening angle: 5 °

Length restriction of incidence Length of slit: 10 mm

Light receiving PSA: None

Light receiving side slit opening angle: 5 °

Monochromator: K? Filter method

Measurement mode: Continuous

Incidence slit width: 0.5 °

Receiving slit width: 20mm

Measurement range (2?): 5 to 70 °

Sampling width (2?): 0.01 °

Scan speed: 20 ° / min

When the active material to be measured is contained in the electrode material of the non-aqueous electrolyte cell, first, the electrode is taken out from the non-aqueous electrolyte cell by the above-described procedure, and the electrode thus taken out is cleaned by the area of the holder of the powder X- And cut into a measurement sample.

Measurements are made by attaching the obtained measurement sample directly to the glass holder. At this time, the peaks of the mixture such as the current collector foil, the conductive auxiliary agent and the binder are measured in advance using XRD, and the peak positions derived therefrom are grasped. When there are peaks overlapping with the active material particles, it is necessary to separate peaks other than the active material particles. When the peak of the substrate overlaps with the peak of the active material, it is preferable that the layer containing the active material (for example, an electrode layer described later) is peeled off from the substrate and provided for measurement. This is because, when the peak intensity is measured quantitatively, the overlapped peaks are separated.

Thus, wide angle X-ray diffraction measurement of the active material contained in the battery can be performed. In order to collect the data for the Rietveld, the step width is set to 1/3 to 1/5 of the minimum half width of the diffraction peak, and the intensity of the peak at the peak position of the strongest reflection is appropriately determined to be 5000 cps or more. Adjust the line strength.

According to the first embodiment, a battery active material is provided. The battery active material includes active material particles of a monoclinic niobium titanium composite oxide. The monoclinic niobium titanium composite oxide contains at least one kind of element selected from the group consisting of Mo, V and W. The content of at least one element selected from the group consisting of Mo, V and W in the monoclinic niobium titanium composite oxide is in the range of 0.01 atm% to 2 atm%. In the active material particle, the aspect ratio of the primary particles is in the range of 1 to less than 4. The crystallite size of the active material particles is in the range of 5 nm or more and 90 nm or less. This battery active material is capable of suppressing generation of an overvoltage upon charging and a side reaction at the reduction side when used in a built-in nonaqueous electrolyte battery because the diffusion length of the Li solid in the active material particle during crystal growth is suppressed. As a result, the battery active material according to the first embodiment can realize a nonaqueous electrolyte battery excellent in input / output characteristics and cycle characteristics.

(Second Embodiment)

According to the second embodiment, a nonaqueous electrolyte battery is provided. The nonaqueous electrolyte battery includes a negative electrode, a positive electrode, and a nonaqueous electrolyte. The negative electrode includes the battery active material according to the first embodiment.

The nonaqueous electrolyte battery according to the second embodiment may further include a separator disposed between the positive electrode and the negative electrode. The positive electrode, the negative electrode and the separator can constitute an electrode group. The nonaqueous electrolyte can be held in the electrode group.

In addition, the non-aqueous electrolyte cell according to the second embodiment may further include an electrode assembly and an external member for accommodating the non-aqueous electrolyte.

The nonaqueous electrolyte battery according to the second embodiment may further include a positive electrode terminal electrically connected to the positive electrode and a negative electrode terminal electrically connected to the negative electrode. At least a part of the positive electrode terminal and at least a part of the negative electrode terminal can extend outside the exterior member.

Hereinafter, the positive electrode, negative electrode, nonaqueous electrolyte, separator, outer member, positive electrode terminal and negative electrode terminal will be described in detail.

1) positive

The positive electrode may include a current collector and a positive electrode layer (positive electrode active material containing layer). The positive electrode layer may be formed on one side or both sides of the current collector. The positive electrode layer may include a positive electrode active material, and optionally, a conductive agent and a binder.

As the positive electrode active material, for example, oxides, sulfides, polymers and the like can be used.

Examples of the oxides and sulfides which can be used include manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, Li _x Mn ₂ O ₄ Or Li _x MnO ₂ ), a lithium nickel complex oxide (for example, Li _x NiO ₂ ), a lithium cobalt complex oxide (for example, Li _x CoO ₂ ), a lithium nickel cobalt complex oxide (for example, LiNi _{1 - y} Co _y O _2), lithium manganese cobalt composite oxide (e.g. _{Li x Mn y Co 1 -y O} 2), lithium manganese nickel complex oxide having a spinel structure (for example, _{Li x Mn 2 - y Ni y} O 4), (E.g., Li _x FePO ₄ , Li _x Fe _{1 - y} Mn _y PO ₄ , Li _x CoPO ₄ ), iron sulfate (Fe ₂ (SO ₄ ) ₃ ), vanadium oxide For example, V ₂ O ₅ ) and lithium nickel cobalt manganese composite oxides. In the above formula, 0 <x? 1 and 0 <y? 1. As the active material, these compounds may be used alone, or a plurality of compounds may be used in combination.

As the polymer, for example, a conductive polymer material such as polyaniline or polypyrrole, or a disulfide-based polymer material can be used. Sulfur (S) and carbon fluoride can also be used as the active material.

Examples of the more preferable positive electrode active material include a lithium manganese composite oxide having a high positive electrode voltage (for example, Li _x Mn ₂ O ₄ ), a lithium nickel composite oxide (for example, Li _x NiO ₂ ), a lithium cobalt complex oxide Li _x CoO _2), lithium nickel cobalt composite oxide (for example, _{LiNi 1 -y Co y O 2)} , lithium manganese nickel complex oxide having a spinel structure (for example, _{Li x Mn 2 - y Ni y} O 4), Lithium manganese cobalt composite oxide (for example, Li _x Mn _y Co _{1 - y} O ₂ ), lithium iron phosphate (for example, Li _x FePO ₄ ), and lithium nickel cobalt manganese composite oxide. In the above formula, 0 <x? 1 and 0 <y? 1.

Among them, in the case of using a non-aqueous electrolyte containing a room temperature molten salt, it is preferable to use lithium iron phosphate, Li _x VPO ₄ F, lithium manganese composite oxide, lithium nickel composite oxide and lithium nickel cobalt composite oxide, . This is because the reactivity between the positive electrode active material and the room temperature molten salt is reduced.

The specific surface area of the positive electrode active material is preferably 0.1 m ² / g or more and 10 m ² / g or less. The positive electrode active material having a specific surface area of 0.1 m ² / g or more can sufficiently insulate and release lithium ions. The positive electrode active material having a specific surface area of 10 m ² / g or less is easily handled in industrial production, and a satisfactory charge-discharge cycle performance can be ensured.

The binder may be blended to fill the gaps of the dispersed positive electrode active material to bind the positive electrode active material and the conductive agent. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine rubber.

The conductive agent is compounded as needed in order to enhance the current collecting performance and to suppress the contact resistance between the positive electrode active material and the current collector. Examples of the conductive agent include carbonaceous materials such as acetylene black, carbon black and graphite.

In the positive electrode layer, it is preferable that the positive electrode active material and the binder are blended in a ratio of 80 wt% or more and 98 wt% or less and 2 wt% or more and 20 wt% or less, respectively.

When the amount of the binder is 2% by weight or more, sufficient electrode strength can be obtained. When the content is 20% by weight or less, the compounding amount of the insulator of the electrode can be reduced and the internal resistance can be reduced. When the conductive agent is added, the positive electrode active material, the binder, and the conductive agent are mixed in a proportion of 77 wt% or more and 95 wt% or less, 2 wt% or more and 20 wt% or less and 3 wt% or more and 15 wt% or less . By setting the amount of the conductive agent to 3 wt% or more, the above-mentioned effect can be exhibited. When the amount is 15% by weight or less, the decomposition of the nonaqueous electrolyte on the surface of the positive electrode conductive agent under high temperature preservation can be reduced.

It is preferable that the positive electrode current collector is an aluminum alloy foil or an aluminum alloy foil containing elements such as Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu and Si. The thickness of the aluminum foil or the aluminum alloy foil is preferably 5 탆 or more and 20 탆 or less, and more preferably 15 탆 or less. The purity of the aluminum foil is preferably 99 wt% or more. The content of transition metals such as iron, copper, nickel, and chromium contained in the aluminum foil or the aluminum alloy foil is preferably 1 wt% or less.

The positive electrode can be produced by, for example, suspending a positive electrode active material, a binder, and a conductive agent, if necessary, in a suitable solvent to prepare a slurry, applying the slurry to the positive electrode current collector and drying the positive electrode layer, . The positive electrode may also be produced by forming a positive electrode active material, a binder and a conductive agent, if necessary, in a pellet form to form a positive electrode layer and then forming this on the current collector.

2) negative polarity

The negative electrode may include a current collector and a negative electrode layer (negative electrode active material containing layer). The negative electrode layer may be formed on one side or both sides of the current collector. The negative electrode layer may include a negative electrode active material, and optionally a conductive agent and a binder.

The battery active material according to the first embodiment may be included in the negative electrode layer as the negative electrode active material.

As described above, in the battery active material according to the first embodiment, an increase in the diffusion length in the Li solid in the active material particles during crystal growth is suppressed. Therefore, the nonaqueous electrolyte battery having the negative electrode including the battery active material according to the first embodiment can exhibit excellent input / output characteristics and cycle characteristics.

The negative electrode layer may include the active material according to the first embodiment alone as the negative electrode active material, but may further include another negative electrode active material. Examples of other negative electrode active materials include anatase type titanium dioxide TiO ₂ , monoclinic β type titanium dioxide TiO ₂ (B), rhamstellite type lithium titanate Li ₂ Ti ₃ O ₇ , spinel type lithium titanate Li ₄ Ti ₅ O ₁₂ , Niobium oxide and the like can be used. These oxides and composite oxides can be suitably used because they have a specific gravity similar to that of the compound contained in the battery active material according to the first embodiment and are easily mixed and dispersed.

The conductive agent is compounded as needed in order to enhance the current collection performance of the negative electrode active material and to suppress the contact resistance between the negative electrode active material and the current collector. Examples of the conductive agent include carbon materials such as acetylene black, carbon black and graphite.

The binder may be compounded to fill the gaps of the dispersed negative active material so that the negative active material and the electroconductive agent are bound together. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, and styrene butadiene rubber.

The negative electrode active material, the conductive agent and the binder in the negative electrode layer are preferably contained in an amount of 68 wt% or more and 96 wt% or less, 2 wt% or more and 30 wt% or less, and 2 wt% or more and 30 wt% . When the amount of the conductive agent is 2% by weight or more, the current collecting performance of the negative electrode layer is good. When the amount of the binder is 2% by weight or more, the binding property between the negative electrode layer and the current collector is sufficient, and excellent cycle characteristics can be expected. On the other hand, in order to increase the capacity of the nonaqueous electrolyte battery, the amount of the binder is preferably 30% by weight or less.

As the negative electrode collector, a material that is electrochemically stable at the storage and discharge potential of lithium in the negative electrode active material is used. The negative electrode current collector is preferably made of an aluminum alloy containing elements such as copper, nickel, stainless steel or aluminum or an element such as Mg, Ti, Zn, Mn, Fe, Cu and Si. The thickness of the current collector is preferably 5 to 20 mu m. The current collector having such a thickness can balance the strength and weight of the negative electrode.

The negative electrode is produced by, for example, suspending a negative electrode active material, a conductive agent and a binder in a commonly used solvent to prepare a slurry, applying the slurry to a current collector and drying the negative electrode layer to form a negative electrode layer, . The negative electrode may also be produced by forming the negative electrode active material, the conductive agent and the binder in the form of pellets to form a negative electrode layer and then forming the negative electrode layer on the current collector.

3) Non-aqueous electrolyte

The nonaqueous electrolyte may be a liquid nonaqueous electrolyte prepared, for example, by dissolving an electrolyte in an organic solvent, or a gelated nonaqueous electrolyte in which a liquid electrolyte and a polymer material are combined.

The liquid non-aqueous electrolyte is preferably dissolved in an organic solvent at a concentration of 0.5 mol / L or more and 2.5 mol / L or less.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium arsenic fluoride (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), bis-trifluoromethyl sulfonyl include a lithium salt, or a mixture thereof, such as lithium imide _{(LiN (CF 3 SO 2)} 2). It is preferable that the electrolyte is difficult to be oxidized even at a high electric potential, and LiPF ₆ is most preferable.

Examples of the organic solvent include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC) and vinylene carbonate, diethyl carbonate (DEC), dimethyl carbonate (DMC) , Methyl ethyl carbonate (MEC), cyclic ethers such as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2MeTHF), dioxolane (DOX), dimethoxyethane (DME) (GBL), acetonitrile (AN), and sulfolane (SL), which are known to those skilled in the art. These organic solvents may be used singly or in the form of a mixed solvent.

Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO).

Alternatively, the nonaqueous electrolyte may be a room temperature molten salt (ionic flame) containing lithium ion, a polymer solid electrolyte, an inorganic solid electrolyte, or the like.

The room temperature molten salt (ionic flame) refers to a compound that can exist as a liquid at room temperature (15 to 25 ° C) in an organic salt containing a combination of an organic cation and an anion. The room temperature molten salt includes a room-temperature molten salt present as a liquid as a unit, a room-temperature molten salt becoming a liquid by mixing with an electrolyte, and a room-temperature molten salt becoming a liquid by dissolving in an organic solvent. Generally, the melting point of a room temperature molten salt used in a non-aqueous electrolyte cell is 25 占 폚 or lower. Further, the organic cation generally has a quaternary ammonium skeleton.

The polymer solid electrolyte is produced by dissolving an electrolyte in a polymer material and solidifying it.

The inorganic solid electrolyte is a solid material having lithium ion conductivity.

4) Separator

The separator may be formed of, for example, a polyethylene film, a polypropylene film, a cellulose film, or a porous film made of polyvinylidene fluoride (PVdF) or a nonwoven fabric made of a synthetic resin. Among them, the porous film formed of polyethylene or polypropylene can melt at a certain temperature and cut off current, so that safety can be improved.

5) The outer member

A laminate film having a thickness of 0.5 mm or less or a metallic container having a thickness of 1 mm or less can be used for the exterior member. The thickness of the laminated film is more preferably 0.2 mm or less. The metal container is more preferably 0.5 mm or less in thickness, and more preferably 0.2 mm or less in thickness.

The shape of the exterior member may be flat (thin), square, cylindrical, coin, button, or the like. The exterior member can be, for example, an exterior member for a small-sized battery mounted on a portable electronic device or the like, or an exterior member for a large-sized battery mounted on a two- or four-wheeled vehicle, depending on the battery dimension.

As the laminated film, a multilayer film in which a metal layer is sandwiched between resin layers is used. The metal layer is preferably an aluminum foil or an aluminum alloy foil for weight saving. As the resin layer, a polymer material such as polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET) or the like can be used. The laminated film can be formed into a shape of an exterior member by performing sealing by heat fusion.

The metallic container is made of aluminum or an aluminum alloy or the like. The aluminum alloy is preferably an alloy containing elements such as magnesium, zinc, and silicon. When the alloy contains a transition metal such as iron, copper, nickel or chromium, its content is preferably 1% by weight or less. As a result, the long-term reliability and heat dissipation performance under a high-temperature environment can be remarkably improved.

Next, the nonaqueous electrolyte battery according to the second embodiment will be described in more detail with reference to the drawings.

3 is a cross-sectional view of an example flat non-aqueous electrolyte cell according to the second embodiment. 4 is an enlarged sectional view of part A of Fig.

The nonaqueous electrolyte battery 10 shown in Figs. 3 and 4 includes the bag-shaped sheathing member 2 shown in Fig. 3, the electrode group 1 shown in Figs. 3 and 4, the nonaqueous electrolyte Respectively. The electrode assembly 1 and the nonaqueous electrolyte are contained in the outer sheath 2. The non-aqueous electrolyte is held in the electrode group 1.

The bag-shaped sheathing member 2 includes a laminate film including two resin layers and a metal layer sandwiched therebetween.

As shown in Fig. 3, the electrode group 1 is a group of flat-shaped wound electrodes. As shown in Fig. 4, the flat rolled electrode group 1 is formed by laminating the stacked layers in the order of the negative electrode 3, the separator 4, the positive electrode 5, and the separator 4 from the outside, , And press-formed.

The negative electrode 3 includes a negative electrode collector 3a and a negative electrode layer 3b. The negative electrode layer 3b includes the battery active material according to the first embodiment. As shown in Fig. 4, the outermost negative electrode 3 has a structure in which the negative electrode layer 3b is formed only on one side of the inner surface side of the negative electrode collector 3a. In the other negative electrode 3, the negative electrode layer 3b is formed on both surfaces of the negative electrode collector 3a.

The positive electrode 5 includes a positive electrode current collector 5a and positive electrode layers 5b formed on both surfaces thereof.

3, the negative electrode terminal 6 is connected to the negative electrode current collector 3a of the outermost negative electrode 3 in the vicinity of the outer peripheral end of the wound electrode group 1, and the positive electrode terminal 7 And is connected to the positive electrode collector 5a of the positive electrode 5 on the inner side. The negative electrode terminal 6 and the positive electrode terminal 7 extend outward from the opening of the bag-like sheathing member 2.

The nonaqueous electrolyte battery 10 shown in Figs. 3 and 4 can be manufactured by the following procedure, for example. First, the electrode group 1 is fabricated. Subsequently, the electrode assembly 1 is sealed in the bag-shaped sheathing member 2. At this time, the negative electrode terminal 6 and the positive electrode terminal 7 are arranged such that one end of each of the negative electrode terminal 6 and the positive electrode terminal 7 is evacuated to the outside of the outer casing member 2. [ Then, the periphery of the exterior member 2 is heat-sealed while leaving a part thereof. Next, a liquid non-aqueous electrolyte, for example, is injected from the opening of the bag-shaped sheathing member 2 which is not heat-sealed. Lastly, the wound electrode group 1 and the liquid nonaqueous electrolyte are sealed by heat sealing the openings.

The nonaqueous electrolyte battery according to the second embodiment is not limited to the nonaqueous electrolyte battery according to the example shown in Figs. 3 and 4, but may be a battery having the structure shown in Figs. 5 and 6, for example.

5 is a partially cutaway perspective view schematically showing a non-aqueous electrolyte battery according to another example of the second embodiment. 6 is an enlarged cross-sectional view of part B in Fig.

The nonaqueous electrolyte battery 10 shown in Figs. 5 and 6 includes the electrode group 11 shown in Figs. 5 and 6, the sheath member 12 shown in Fig. 5, and a nonaqueous electrolyte not shown. The electrode assembly 11 and the non-aqueous electrolyte are housed in the casing member 12. The non-aqueous electrolyte is held in the electrode group 11.

The sheathing member 12 includes a laminate film including two resin layers and a metal layer interposed therebetween.

The electrode group 11 is a stacked electrode group as shown in Fig. The stacked electrode assembly 11 has a structure in which a positive electrode 13 and a negative electrode 14 are alternately stacked with a separator 15 interposed therebetween as shown in FIG.

The electrode group (11) includes a plurality of positive electrodes (13). Each of the plurality of positive electrodes 13 includes a positive electrode current collector 13a and a positive electrode layer 13b supported on both surfaces of the positive electrode current collector 13a. Further, the electrode group 11 includes a plurality of negative electrodes 14. Each of the plurality of negative electrodes 14 includes a negative electrode collector 14a and a negative electrode layer 14b supported on both surfaces of the negative electrode collector 14a. One side of the negative electrode current collector 14a of each negative electrode 14 protrudes from the negative electrode 14. The protruded anode current collector 14a is electrically connected to the strip-shaped negative electrode terminal 16. The tip end of the strip-shaped negative electrode terminal 16 is drawn out from the exterior member 12 to the outside. Although not shown, the positive electrode current collector 13a of the positive electrode 13 protrudes from the positive electrode 13 located on the opposite side of the protruding side of the negative electrode current collector 14a. The positive electrode current collector 13a protruded from the positive electrode 13 is electrically connected to the strip-shaped positive electrode terminal 17. The tip end of the strip-shaped positive electrode terminal 17 is located on the side opposite to the negative electrode terminal 16 and is drawn out from the side of the sheathing member 12 to the outside.

The nonaqueous electrolyte battery according to the second embodiment includes the negative electrode including the battery active material according to the first embodiment. As a result, the nonaqueous electrolyte battery according to the second embodiment can exhibit excellent input / output characteristics and cycle characteristics.

(Third Embodiment)

According to the third embodiment, a battery pack is provided. This battery pack comprises the nonaqueous electrolyte battery according to the second embodiment.

The battery pack according to the third embodiment may include one or a plurality of non-aqueous electrolyte cells (single cells) according to the second embodiment described above. A plurality of non-aqueous electrolyte batteries which may be included in the battery pack according to the third embodiment may be connected electrically in series or in parallel to constitute a battery module. The battery pack according to the third embodiment may include a plurality of assembled batteries.

Next, an example battery pack according to the third embodiment will be described with reference to the drawings.

7 is an exploded perspective view of an example battery pack according to the third embodiment. 8 is a block diagram showing an electric circuit of the battery pack of Fig.

The battery pack 20 shown in Figs. 7 and 8 includes a plurality of unit cells 21. As shown in Fig. The plurality of unit cells 21 are the flat non-aqueous electrolyte batteries 10 described with reference to Figs.

The plurality of unit cells 21 are stacked in such a manner that the negative terminal 6 and the positive electrode terminal 7 extending outward are aligned in the same direction and are tightened with the adhesive tape 22 to constitute the battery module 23 . These unit cells 21 are electrically connected to each other in series as shown in Fig.

The printed wiring board 24 is disposed so as to face the side surface of the battery module 23 in which the negative terminal 6 and the positive terminal 7 extend. A thermistor 25, a protection circuit 26, and a terminal 27 for external devices are mounted on the printed wiring board 24 as shown in Fig. An insulating plate (not shown) is provided on the surface of the printed wiring board 24 facing the battery module 23 to avoid unnecessary connection with the wiring of the battery module 23.

The positive electrode lead 28 is connected to the positive electrode terminal 7 located at the lowermost layer of the assembled battery 23 and its tip end is inserted into the positive electrode connector 29 of the printed wiring board 24 and electrically connected thereto have. The negative electrode side lead 30 is connected to the negative electrode terminal 6 located on the uppermost layer of the assembled battery 23 and the leading end thereof is inserted and electrically connected to the negative electrode side connector 31 of the printed wiring board 24 have. These connectors 29 and 31 are connected to the protection circuit 26 through the wirings 32 and 33 formed on the printed wiring board 24.

The thermistor 25 detects the temperature of the unit cell 21, and the detection signal is transmitted to the protection circuit 26. [ The protection circuit 26 can cut off the positive side wiring 34a and the negative side wiring 34b between the protection circuit 26 and the transmission terminal 27 to the external device under a predetermined condition. The predetermined condition is, for example, when the temperature detected by the thermistor 25 becomes equal to or higher than a predetermined temperature. Another example of the predetermined condition is the case where overcharge, overdischarge, overcurrent, or the like of the unit cell 21 is detected. Detection of the overcharging or the like is performed for the individual unit cells 21 or the whole battery module 23. When detecting the individual unit cells 21, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode to be used as a reference electrode is inserted into each of the unit cells 21. In the case of the battery pack 20 shown in Figs. 7 and 8, the wiring 35 for voltage detection is connected to each of the unit cells 21, and a detection signal is supplied to the protection circuit 26 through these wirings 35 .

A protective sheet 36 made of rubber or resin is disposed on each of three side surfaces of the battery module 23 except the side where the positive electrode terminal 7 and the negative electrode terminal 6 protrude.

The battery pack 23 is accommodated in the storage container 37 together with the protective sheet 36 and the printed wiring board 24. That is, the protective sheet 36 is disposed on each of the inner side surfaces in the long side direction and the short side direction of the storage container 37, and the printed wiring board 24 is disposed on the inner side opposite to the short side direction . The assembled battery 23 is placed in a space surrounded by the protective sheet 36 and the printed wiring board 24. The lid 38 is provided on the upper surface of the storage container 37.

In place of the adhesive tape 22, a heat-shrinkable tape may be used for fixing the battery module 23. In this case, a protective sheet is disposed on both side surfaces of the assembled battery, the heat-shrinkable tube is circulated, and the heat-shrinkable tube is thermally contracted to bind the assembled battery.

In FIGS. 7 and 8, the plurality of unit cells 21 are connected in series, but they may be connected in parallel in order to increase the battery capacity. Alternatively, a serial connection and a parallel connection may be combined. The assembled battery packs may be connected again in series or in parallel.

The shape of the battery pack according to the third embodiment is suitably changed according to the use. The battery pack according to the third embodiment is suitably used for applications requiring excellent cycle characteristics when a large current is taken out. Specifically, it is used as a power source of a digital camera or as a hybrid vehicle for two or four-wheel vehicles, an electric vehicle for two or four wheels, and a vehicle-mounted battery for an electric bicycle, for example. In particular, it is suitably used as an in-vehicle battery.

The battery pack according to the third embodiment includes the nonaqueous electrolyte battery according to the second embodiment. As a result, the battery pack according to the third embodiment can exhibit excellent input / output characteristics and cycle characteristics.

[Example]

EXAMPLES Hereinafter, the embodiments will be described in more detail based on examples, but the invention is not limited to the examples described below unless it exceeds the gist of the invention.

(Example 1)

In Example 1, the active material of Example 1 was synthesized by the following procedure.

First, as a starting material, a titanyl sulfuric acid sulfuric acid solution having a molar concentration of Ti of 1.28 mol / L, an ethanol solution of niobium chloride having a molar concentration of Nb of 0.5 mol / L and a molybdenum chloride solution having a molar concentration of Mo of 0.5 mol / L An ethanol solution of molybdenum chloride was prepared.

Subsequently, these solutions were mixed to obtain a transparent mixed solution free from precipitation of foreign matters such as hydroxides. The mixing was performed so that the molar ratio Ti: Nb: Mo was 1.0: 2.18: 0.05.

Subsequently, ammonia water was added dropwise to the mixed solution with stirring to adjust the pH of the solution to 8. By the dropwise addition of ammonia water, a white precipitate was generated in the mixed solution. This precipitate was taken out from the mixed solution, washed with pure water, and recovered by filtration. Subsequently, the precipitate thus recovered was dried with a heater at 80 ° C. Thereafter, agglomeration of the precipitate was broken by a planetary ball mill. Thereafter, this precipitate was fired at 900 ° C for 30 minutes under atmospheric conditions. At this time, the temperature raising rate was 30 占 폚 / min. Thereafter, the product obtained by firing was pulverized by a planetary ball mill to obtain a powder. This powder was used as the active material of Example 1.

A small amount of the active material of Example 1 was measured, and acid dissolution and alkali dissolution were carried out to prepare a measurement solution. Using this measurement solution, the amount of each element of Ti, Nb and Mo per unit weight of the active material of Example 1 was calculated by performing ICP analysis (SPS-3520UV manufactured by SII Nanotechnology Co., Ltd.). On the other hand, a small amount of the active material of Example 1 was further measured to prepare another measurement solution, which was then subjected to analysis by an inert gas-infrared absorption method (TC-600, manufactured by LECO) The amount of O element per unit weight was calculated. From these results, it was found that the molar ratio of each constituent element contained per unit weight of the active material of Example 1 was calculated. As a result, it was found that Ti = 10.086 atm%, Nb = 19.976 atm%, Mo = 0.012 atm%, O = 69.926 atm% .

Further, the powder of the active material of Example 1 was subjected to wide angle X-ray diffraction measurement. The spectrum is shown in Fig. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. The obtained spectrum was subjected to fitting by performing automatic profile processing using analysis software &quot; Rigaku PDXL2 ver.2.1 &quot;. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the active material particle included in the active material of Example 1 had a crystallite size of 30.1 nm.

The SEM image of the active material of Example 1 was also photographed. The apparatus used was SU-8020 manufactured by Hitachi High-Technologies Corporation. Concretely, a carbon tape was stuck on the sample stage, the powder collected at the end of the swab was lightly placed on the sample, and the sample was compressed and blown with air to blow off excess powder. Observation conditions were an acceleration voltage of 3 kV, a probe condition of 10 A, and a magnification of 20,000 times. A representative SEM image is shown in Fig. From this SEM image, primary particles having the highest aspect ratio were selected. The aspect ratio is the ratio B / A when the particle diameter in the direction of the shortest particle diameter of the primary particles is A and the particle diameter of the longest direction is B. The aspect ratio of the particles with the highest aspect ratio on the SEM of Fig. 10 was 1.40. The same operation was carried out using 30 sheets of SEM images and the average thereof was calculated as the aspect ratio of the primary particles of the active material particles contained in the active material of Example 1 (calculated by rounding off the third decimal place). As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 1 was 1.52.

(Example 2)

In Example 2, the active material of Example 2 was synthesized in the same manner as in Example 1 except that the starting material was mixed to obtain a mixed solution, and the molar ratio Ti: Nb: Mo was changed to 1.02: 2.13: 0.10. Respectively.

The molar ratio of each constituent element per unit weight was calculated for the active material of Example 2 in the same manner as in Example 1. As a result, Ti = 10.261 atm%, Nb = 19.587 atm%, Mo = 0.26 atm% , And O = 69.892 atm%.

In addition, the active material of Example 2 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Example 2 was 32.1 nm.

Further, with respect to the active material of Example 2, 30 sheets of SEM images were photographed under the same observation conditions as in Example 1. From these SEM images, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 2 was 1.55.

(Example 3)

In Example 3, the active material of Example 3 was synthesized in the same manner as in Example 1 except that the starting material was mixed to obtain a mixed solution, and the molar ratio Ti: Nb: Mo was changed to 1.05: 2.07: 0.15. Respectively.

The molar ratio of each constituent element per unit weight was calculated for the active material of Example 3 in the same manner as in Example 1. As a result, Ti = 10.435 atm%, Nb = 18.883 atm%, Mo = 1.113 atm% , And O = 69.569atm%.

The active material of Example 3 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Example 3 was 38.9 nm.

Further, for the active material of Example 3, 30 pieces of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 3 was 1.63.

(Example 4)

In Example 4, the active material of Example 4 was synthesized in the same manner as in Example 1, except that the starting materials were mixed to obtain a mixed solution and the molar ratio Ti: Nb: Mo was changed to 1.05: 2.07: 0.20. Respectively.

The molar ratio of each constituent element contained per unit weight was calculated for the active material of Example 4 in the same manner as in Example 1. As a result, Ti = 10.348 atm%, Nb = 18.725 atm%, Mo = 1.941 atm% , And O = 68.986atm%.

The active material of Example 4 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak belonging to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the crystallite size is calculated by using Scherr's equation Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Example 4 was 42.3 nm.

Further, for the active material of Example 4, 30 pieces of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 4 was 1.71.

(Example 5)

In Example 5, the active material of Example 5 was synthesized in the same manner as in Example 2 except that the sintering temperature was 800 캜.

The molar ratio of each constituent element contained per unit weight was calculated for the active material of Example 5 in the same manner as in Example 1. As a result, Ti = 10.261 atm%, Nb = 19.587 atm%, Mo = 0.26 atm% , And O = 69.892 atm%.

In addition, the active material of Example 5 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the active material particle included in the active material of Example 5 had a crystallite size of 20.6 nm.

Further, for the active material of Example 5, 30 sheets of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 5 was 1.42.

(Example 6)

In Example 6, the active material of Example 6 was synthesized in the same manner as in Example 2 except that the firing temperature was 700 캜.

The molar ratio of each constituent element per unit weight was calculated for the active material of Example 6 in the same manner as in Example 1. As a result, Ti = 10.261 atm%, Nb = 19.587 atm%, Mo = 0.26 atm% , And O = 69.892 atm%.

The active material of Example 6 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the active material particle included in the active material of Example 6 had a crystallite size of 10.1 nm.

Further, for the active material of Example 6, 30 pieces of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 6 was 1.21.

(Example 7)

In Example 7, the active material of Example 7 was synthesized in the same manner as in Example 2, except that the heating rate at firing was 40 ° C / min.

The molar ratio of each constituent element per unit weight was calculated for the active material of Example 7 in the same manner as in Example 1. As a result, Ti = 10.261 atm%, Nb = 19.587 atm%, Mo = 0.26 atm% , And O = 69.892 atm%.

Further, the active material of Example 7 was subjected to wide-angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Example 7 was 30.2 nm.

Further, for the active material of Example 7, 30 SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 7 was 1.21.

(Example 8)

In Example 8, the active material of Example 8 was synthesized in the same manner as in Example 2, except that the heating rate at the time of firing was 25 ° C / min.

The molar ratio of each constituent element per unit weight was calculated for the active material of Example 8 in the same manner as in Example 1. As a result, Ti = 10.261 atm%, Nb = 19.587 atm%, Mo = 0.26 atm% , And O = 69.892 atm%.

The active material of Example 8 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Example 8 was 32.6 nm.

Further, for the active material of Example 8, 30 pieces of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 8 was 2.65.

(Example 9)

In Example 9, the active material of Example 9 was synthesized in the same manner as in Example 2, except that the heating rate at firing was 20 ° C / min.

The molar ratio of each constituent element per unit weight was calculated for the active material of Example 9 in the same manner as in Example 1. As a result, Ti = 10.261 atm%, Nb = 19.587 atm%, Mo = 0.26 atm% , And O = 69.892 atm%.

The active material of Example 9 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Example 9 was 29.5 nm.

For the active material of Example 9, 30 sheets of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 9 was 3.82.

(Example 10)

In Example 10, the active material of Example 10 was synthesized by the following procedure.

First, a titanyl sulfuric acid sulfuric acid solution having a molar concentration of Ti of 1.28 mol / L as a starting material, an ethanol solution of niobium chloride having a molar concentration of Nb of 0.5 mol / L, and a chloride An ethanol solution of tungsten was prepared.

Subsequently, these solutions were mixed to obtain a transparent mixed solution free from precipitation of foreign matters such as hydroxides. The mixing was carried out such that the molar ratio Ti: Nb: W was 1.0: 2.18: 0.02.

Subsequently, ammonia water was added dropwise to the mixed solution with stirring to adjust the pH of the solution to 8. By the dropwise addition of ammonia water, a white precipitate was generated in the mixed solution. The precipitate was taken out from the mixed solution, washed with pure water, and recovered by filtration. Subsequently, the precipitate thus recovered was dried with a heater at 80 ° C. Thereafter, agglomeration of the precipitate was broken by a planetary ball mill. Thereafter, this precipitate was fired at 900 DEG C for 30 minutes under atmospheric conditions. At this time, the temperature raising rate was 30 占 폚 / min. Thereafter, the product obtained by firing was pulverized by a planetary ball mill to obtain a powder. This powder was used as the active material of Example 10.

A small amount of the active material of Example 10 was measured, and acid dissolution and alkali dissolution were carried out to prepare a measurement solution. Using this measurement solution, ICP analysis (SPS-3520UV, manufactured by SII Nanotechnology Co., Ltd.) was performed to calculate the amount of each element of Ti, Nb and W per unit weight with respect to the active material of Example 10. [ On the other hand, a small amount of the active material of Example 10 was further measured to prepare another measurement solution, which was then subjected to analysis by an inert gas-infrared absorption method (TC-600, manufactured by LECO) The amount of O element per unit weight was calculated. From these results, it was found that the molar ratios of the constituent elements contained in the active material of Example 10 per unit weight were calculated. As a result, Ti = 10.09 atm%, Nb = 19.978 atm%, W = 0.011 atm%, O = 69.921 atm% .

The active material of Example 10 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the active material particle contained in the active material of Example 10 had a crystallite size of 29.5 nm.

Further, for the active material of Example 10, 30 sheets of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 10 was 1.58.

(Example 11)

In Example 11, the active material of Example 11 was synthesized in the same manner as in Example 10 except that the starting material was mixed to obtain a mixed solution, and the molar ratio Ti: Nb: W was changed to 1.04: 2.1: 0.05. Respectively.

The molar ratio of each constituent element per unit weight was calculated for the active material of Example 11 in the same manner as in Example 1. As a result, Ti = 10.47 atm%, Nb = 19.161 atm%, W = 0.47 atm% , And O = 69.899atm%.

The active material of Example 11 was subjected to wide-angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak belonging to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the crystallite size is calculated using the Scherr's equation Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Example 11 was 31.9 nm.

For the active material of Example 11, 30 sheets of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 11 was 1.62.

(Example 12)

In Example 12, the active material of Example 12 was synthesized in the same manner as in Example 10 except that the starting material was mixed to obtain a mixed solution, and the molar ratio Ti: Nb: W was changed to 1.04: 2.1: 0.05. Respectively.

The molar ratio of each constituent element contained per unit weight was calculated for the active material of Example 12 in the same manner as in Example 1. As a result, Ti = 10.36 atm%, Nb = 18.752 atm%, W = 1.796 atm% , And O = 69.088atm%.

The active material of Example 12 was subjected to wide-angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Example 12 was 34.7 nm.

Further, for the active material of Example 12, 30 pieces of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 12 was 1.83.

(Example 13)

In Example 13, the active material of Example 13 was synthesized by the following procedure.

First, a titanyl sulfuric acid sulfuric acid solution having a molar concentration of Ti of 1.28 mol / L as a starting material, an ethanol solution of niobium chloride having a molar concentration of Nb of 0.5 mol / L and a trihydrochloric acid solution having a molar concentration of V of 0.5 mol / An ethanol solution of vanadium oxide was prepared.

Subsequently, these solutions were mixed to obtain a mixed solution free from precipitation of foreign matters such as hydroxides. The mixing was carried out such that the molar ratio Ti: Nb: V was 1.0: 2.15: 0.06.

Then, with stirring, ammonia water was added dropwise to this mixed solution to adjust the pH of the solution to 8. By the dropwise addition of ammonia water, a white precipitate was generated in the mixed solution.

Since the vanadium trichloride as the starting material has high reactivity with water, the above-described mixing of the starting materials and the generation of the white precipitate was carried out under the dew point condition of -30 占 폚 dp.

The precipitate was taken out from the mixed solution, washed with pure water, and recovered by filtration. Subsequently, the thus obtained precipitate was dried with a heater at 80 캜. Thereafter, agglomeration of the precipitate was broken by a planetary ball mill. Thereafter, this precipitate was fired at 900 DEG C for 30 minutes under atmospheric conditions. At this time, the temperature raising rate was 30 캜 / min. Thereafter, the product obtained by firing was pulverized by a planetary ball mill to obtain a powder. This powder was used as the active material of Example 13.

A small amount of the active material of Example 13 was measured and taken out, and acid dissolution and alkali dissolution were carried out to prepare a measurement solution. Using this measurement solution, the amount of each element of Ti, Nb and V per unit weight of the active material of Example 13 was calculated by performing ICP analysis (SPS-3520UV manufactured by SII Nanotechnology Co., Ltd.). On the other hand, a small amount of the active material of Example 13 was further measured to prepare another measurement solution, which was then subjected to analysis by an inert gas-infrared absorption method (TC-600, manufactured by LECO) The amount of O element per unit weight was calculated. From these results, it was found that the molar ratios of the constituent elements contained in the active material of Example 13 per unit weight were calculated. As a result, Ti = 9.99 atm%, Nb = 19.987 atm%, V = 0.013 atm%, O = .

In addition, the active material of Example 13 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Example 13 was 31.6 nm.

Further, for the active material of Example 13, 30 sheets of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 13 was 1.32.

(Example 14)

In Example 14, the active material of Example 14 was synthesized in the same manner as in Example 13 except that the starting material was mixed to obtain a mixed solution and the molar ratio Ti: Nb: V was changed to 1.0: 2.12: 0.10. Respectively.

The molar ratio of each constituent element per unit weight was calculated for the active material of Example 14 in the same manner as in Example 1. As a result, Ti = 10.02 atm%, Nb = 19.4 atm%, V = 0.60 atm% , And O = 69.98 atm%.

The active material of Example 14 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Example 14 was 33.3 nm.

Further, for the active material of Example 14, 30 sheets of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 14 was 1.44.

(Example 15)

In Example 15, the active material of Example 15 was synthesized in the same manner as in Example 13 except that the starting material was mixed to obtain a mixed solution and the molar ratio Ti: Nb: V was changed to 1.0: 2.0: 0.15. Respectively.

The molar ratio of each constituent element per unit weight was calculated for the active material of Example 15 in the same manner as in Example 1. As a result, Ti = 9.907 atm%, Nb = 18.823 atm%, V = 1.922 atm% , And O = 69.348atm%.

The active material of Example 15 was subjected to wide-angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particles contained in the active material of Example 15 was 43.1 nm.

Further, for the active material of Example 15, 30 sheets of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Example 15 was 1.59.

(Comparative Example 1)

In Comparative Example 1, TiNb ₂ O ₇ , which is the active material of Comparative Example 1, was synthesized by the solid phase method described below.

First, titanium oxide powder, niobium oxide powder, and molybdenum oxide powder were prepared. These powders were weighed so that the molar ratio Ti: Nb: Mo was 1.05: 1.9: 0.08. These powders were wet-mixed by a planetary ball mill to obtain a mixture. Ethanol was used as a solvent. The resulting mixture was taken out and dried with a heater at 80 DEG C, and the solvent was evaporated from the mixture. Thereafter, the mixture was subjected to the firing at 1000 占 폚 over 12 hours in an air atmosphere. Subsequently, the plasticizer was naturally cooled. Thereafter, the calcined material was put in a planetary ball mill again and subjected to pulverization and mixing to obtain a precursor. This precursor was subjected to heat treatment at 1000 占 폚 for 12 hours. Thereafter, the fired product was pulverized again with a planetary ball mill to break coarse particles. Thus, an active material powder of Comparative Example 1 was obtained.

The molar ratio of each constituent element per unit weight was calculated for the active material of Comparative Example 1 in the same manner as in Example 1. As a result, Ti = 10.498 atm%, Nb = 18.996 atm%, Mo = 0.520 atm% , And O = 69.986atm%.

In addition, the active material of Comparative Example 1 was subjected to wide-angle X-ray diffraction measurement in the same manner as in Example 1. The spectrum is shown in Fig. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Comparative Example 1 was 85.3 nm.

In addition, for the active material of Comparative Example 1, 30 SEM images were photographed in the same manner as in Example 1 except that the observation magnification was changed to 5000 times. A representative SEM image is shown in Fig. Here, the primary particles having the largest particle diameters were selected and the aspect ratio was calculated to be 4.13. The same operation was carried out using 30 sheets of SEM images, and the average thereof was calculated as the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 1 (calculated by rounding off the third decimal place). As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 1 was 4.50.

(Comparative Example 2)

In Comparative Example 2, tungsten oxide powder, titanium oxide powder, niobium oxide powder and tungsten oxide powder were weighed so that the molar ratio of Ti: Nb: W was 1.05: 1.9: 0.05 instead of molybdenum oxide powder , An active material of Comparative Example 2 was synthesized by the same method as that of Comparative Example 1.

The molar ratio of each constituent element per unit weight was calculated for the active material of Comparative Example 2 in the same manner as in Example 1. As a result, Ti = 10.508 atm%, Nb = 19.02 atm%, W = 0.490 atm% , And O = 69.982atm%.

The active material of Comparative Example 2 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particles contained in the active material of Comparative Example 2 was 90.5 nm.

Further, for the active material of Comparative Example 2, 30 sheets of SEM images were photographed under the same observation conditions as in Comparative Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 2 was 4.23.

(Comparative Example 3)

In Comparative Example 3, a powder of vanadium oxide, a powder of niobium oxide, and a powder of vanadium oxide were mixed at a molar ratio of Ti: Nb: V of 1.0: 1.95: 0.10 in place of molybdenum oxide powder, The active material of Comparative Example 3 was synthesized in the same manner as in Comparative Example 1, except that it was weighed as much as possible.

The molar ratio of each constituent element per unit weight was calculated for the active material of Comparative Example 3 in the same manner as in Example 1. As a result, Ti = 9.968 atm%, Nb = 19.49 atm%, V = 0.510 atm% , And O = 70.032 atm%.

The active material of Comparative Example 3 was subjected to wide-angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particles contained in the active material of Comparative Example 3 was 88.9 nm.

Further, with respect to the active material of Comparative Example 3, 30 sheets of SEM images were photographed under the same observation conditions as in Comparative Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 3 was 4.81.

(Comparative Example 4)

In Comparative Example 4, an active material was synthesized by the same method as in Example 2 except that the firing temperature was 1000 캜.

The molar ratio of each constituent element per unit weight was calculated for the active material of Comparative Example 4 in the same manner as in Example 1. As a result, Ti = 10.261 atm%, Nb = 19.587 atm%, Mo = 0.26 atm% , And O = 69.892 atm%.

The active material of Comparative Example 4 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Comparative Example 4 was 92.1 nm.

Further, for the active material of Comparative Example 4, 30 pieces of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 4 was 3.84.

(Comparative Example 5)

In Comparative Example 5, the active material of Comparative Example 5 was synthesized in the same manner as in Example 2 except that the sintering temperature was 600 캜.

The molar ratio of each constituent element per unit weight was calculated for the active material of Comparative Example 5 in the same manner as in Example 1. As a result, Ti = 10.261 atm%, Nb = 19.587 atm%, Mo = 0.26 atm% , And O = 69.892 atm%.

The active material of Comparative Example 5 was subjected to wide-angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particles contained in the active material of Comparative Example 5 was 4.84 nm.

Further, for the active material of Comparative Example 5, 30 sheets of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 5 was 1.12.

(Comparative Example 6)

In Comparative Example 6, the active material of Comparative Example 6 was synthesized in the same manner as in Example 2, except that the heating temperature at firing was 5 ° C / min.

The molar ratio of each constituent element per unit weight was calculated for the active material of Comparative Example 6 in the same manner as in Example 1. As a result, Ti = 10.261 atm%, Nb = 19.587 atm%, Mo = 0.26 atm% , And O = 69.892 atm%.

In addition, the active material of Comparative Example 6 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Comparative Example 6 was 56.1 nm.

Further, for the active material of Comparative Example 6, 30 SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 6 was 4.21.

(Comparative Example 7)

In Comparative Example 7, the active material of Comparative Example 7 was synthesized in the same manner as in Example 2, except that the heating temperature at firing was 5 ° C / min and the firing temperature was 1000 ° C.

The molar ratio of each constituent element per unit weight was calculated for the active material of Comparative Example 7 in the same manner as in Example 1. As a result, Ti = 10.261 atm%, Nb = 19.587 atm%, Mo = 0.26 atm% , And O = 69.892 atm%.

Further, the active material of Comparative Example 7 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Comparative Example 7 was 85.4 nm.

Further, for the active material of Comparative Example 7, 30 SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 7 was 4.88.

(Comparative Example 8)

In Example 8, the active material of Comparative Example 8 was synthesized in the same manner as in Example 1 except that the starting material was mixed to obtain a mixed solution, and the molar ratio Ti: Nb: Mo was changed to 1.03: 2.02: 0.4. Respectively.

The molar ratio of each constituent element per unit weight was calculated for the active material of Comparative Example 8 in the same manner as in Example 1. As a result, Ti = 10.327 atm%, Nb = 18.686 atm%, Mo = 0.214 atm% , And O = 68.843 atm%.

The active material of Comparative Example 8 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. Some of the peaks of the spectra were consistent with monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C2 / m. However, the above peaks were confirmed. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Comparative Example 8 was 51.5 nm.

Further, for the active material of Comparative Example 8, 30 SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 8 was 1.96.

(Comparative Example 9)

In Comparative Example 9, the active material of Comparative Example 9 was synthesized in the same manner as in Example 1, except that the molar ratio Ti: Nb: Mo was changed to 1.03: 2.02: 0.03 when the starting material was mixed to obtain a mixed solution. Respectively.

The molar ratio of each constituent element per unit weight was calculated for the active material of Comparative Example 9 in the same manner as in Example 1. As a result, it was found that Ti = 10.0 atm%, Nb = 20.0 atm%, Mo = 0.006 atm% , And O = 69.994%.

In addition, the active material of Comparative Example 9 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Comparative Example 9 was 29.9 nm.

Further, for the active material of Comparative Example 9, 30 SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 9 was 1.21.

(Comparative Example 10)

In Comparative Example 10, the active material of Comparative Example 10 was synthesized in the same manner as in Example 10 except that the starting material was mixed to obtain a mixed solution, and the molar ratio Ti: Nb: W was changed to 1.0: 2.1: 0.4. Respectively.

The molar ratio of each constituent element per unit weight was calculated for the active material of Comparative Example 10 in the same manner as in Example 1. As a result, Ti = 10.339 atm%, Nb = 18.708 atm%, W = 2.028 atm% , And O = 68.925 atm%.

The active material of Comparative Example 10 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. Some of the peaks of the spectra were consistent with monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C2 / m. However, the above peaks were confirmed. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particles contained in the active material of Comparative Example 10 was 50.9 nm.

Further, for the active material of Comparative Example 10, 30 sheets of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 10 was 1.77.

(Comparative Example 11)

In Comparative Example 11, the active material of Comparative Example 11 was synthesized in the same manner as in Example 10 except that the starting material was mixed to obtain a mixed solution, and the molar ratio Ti: Nb: W was changed to 1.0: 2.15: 0.1. Respectively.

The molar ratio of each constituent element per unit weight was calculated for the active material of Comparative Example 11 in the same manner as in Example 1. As a result, Ti = 9.999 atm%, Nb = 19.998 atm%, W = 0.008 atm% , And O = 69.994 atm%.

In addition, the active material of Comparative Example 11 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particles contained in the active material of Comparative Example 11 was 28.4 nm.

Further, for the active material of Comparative Example 11, 30 SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 11 was 1.15.

(Comparative Example 12)

In Comparative Example 12, the active material of Comparative Example 12 was synthesized in the same manner as in Example 13, except that the starting material was mixed to obtain a mixed solution and the molar ratio Ti: Nb: V was changed to 1.0: 2.15: 0.4. Respectively.

The molar ratio of each constituent element per unit weight was calculated for the active material of Comparative Example 12 in the same manner as in Example 1. As a result, Ti = 9.798 atm%, Nb = 19.596 atm%, V = 2.018 atm% , And O = 68.587atm%.

The active material of Comparative Example 12 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particle contained in the active material of Comparative Example 12 was 56.8 nm.

Further, for the active material of Comparative Example 12, 30 sheets of SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 12 was 1.82.

(Comparative Example 13)

In Comparative Example 13, the active material of Comparative Example 13 was synthesized in the same manner as in Example 13 except that the starting material was mixed to obtain a mixed solution, and the molar ratio Ti: Nb: V was changed to 1.0: 2.15: 0.03. Respectively.

The molar ratio of each constituent element per unit weight was calculated for the active material of Comparative Example 13 in the same manner as in Example 1. As a result, Ti = 10.0 atm%, Nb = 20.0 atm%, V = 0.003 atm% , And O = 69.997 atm%.

In addition, the active material of Comparative Example 13 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particles contained in the active material of Comparative Example 13 was 28.9 nm.

Further, for the active material of Comparative Example 13, 30 SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 13 was 1.11.

(Comparative Example 14)

Comparative Example 14 was the same as Example 1 except that the ethanol solution of molybdenum chloride was not used as the starting material and that the molar ratio Ti: Nb was changed to 1.0: 2.15 when the starting materials were mixed. The active material of Example 14 was synthesized.

The molar ratio of each constituent element contained per unit weight was calculated for the active material of Comparative Example 14 in the same manner as in Example 1. As a result, Ti = 10.0 atm%, Nb = 20.0 atm%, O = .

The active material of Comparative Example 14 was subjected to wide angle X-ray diffraction measurement in the same manner as in Example 1. The overall peak of the spectrum coincided with the monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, and it was confirmed that the above peak did not appear. For the obtained spectrum, fitting was carried out by the same method as in Example 1. From the half width of the peak attributed to the (110) plane of monoclinic TiNb ₂ O ₇ (PDF: 01-077-1374) belonging to the space group of C 2 / m, the Scherr's equation was used as described above, Respectively. As a result, it was found that the crystallite size of the active material particles contained in the active material of Comparative Example 14 was 20.1 nm.

Further, for the active material of Comparative Example 14, 30 SEM images were photographed under the same observation conditions as in Example 1. From this SEM image, the average aspect ratio (calculated by rounding off the third decimal place) was derived by the same method as in Example 1. [ As a result, it was found that the aspect ratio of the primary particles of the active material particles contained in the active material of Comparative Example 14 was 1.21.

[Preparation of test battery]

Using the synthesized active materials as described above, the test batteries of Examples 1 to 15 and Comparative Examples 1 to 14 were produced according to the following procedure. In the following, the production procedure of the test cell of Example 1 will be described as an example, but other test cells are also manufactured in the same procedure.

<Fabrication of negative electrode>

10% by mass of acetylene black as a conductive auxiliary agent and 10% by mass of carbon nanofibers and 10% by mass of polyvinylidene fluoride (PVdF) as a binder were dissolved in N-methylpyrrolidone (NMP ) To prepare a slurry. This slurry was applied to both surfaces of a current collector including an aluminum foil having a thickness of 12 mu m. At this time, no slurry was applied to a part of the current collector. The coating was then dried and subsequently pressed. Thus, the electrode of Example 1 was produced. The weight per electrode unit area was 60 ± 2 g / m ² (collector-free). The negative electrode of Example 1 had a negative electrode current collector and a negative electrode layer carried thereon. Further, the negative electrode current collector included a negative electrode tab that did not carry the negative electrode layer on its surface.

&Lt; Preparation of positive electrode &

As a positive electrode active material LiNi _{0 .5} Co _{0 .2} Mn _{0 .3} O ₂ powder to 100 mass%, 10 mass% of acetylene black as a conductive auxiliary agent and the carbon nanofibers 10% by weight, as a binder, polyvinylidene fluoride (PVdF) 10 parts % Was added to N-methylpyrrolidone (NMP) and mixed to prepare a slurry. This slurry was applied to both surfaces of a current collector including an aluminum foil having a thickness of 12 mu m. At this time, no slurry was applied to a part of the current collector. The coating was then dried and subsequently pressed. Thus, a positive electrode was produced. The weight per unit area of the positive electrode (g / m ² ) (excluding the current collector) is adjusted so that the ratio of the positive electrode charging capacity A (mAh / g) to the negative electrode charging capacity B (mAh / g) becomes A / B = 1.0 ± 0.05 Respectively. The prepared positive electrode had a positive electrode current collector and a positive electrode layer carried thereon. Further, the positive electrode collector included a positive electrode tab that did not carry the positive electrode layer on its surface.

&Lt; Fabrication of Electrode Group &

Using the negative electrode and the positive electrode thus manufactured, the electrode group shown in Fig. 13 was fabricated by the following procedure. The electrode group shown in Fig. 13 is a part of the electrode group of the test battery of Example 1. Fig.

First, a strip-shaped cellulosic separator 4 was prepared. As shown in Fig. 13, the separator 4 was made to be a vernacular. Subsequently, one negative electrode 3 was laminated on the uppermost layer of the separator 4 which was formed into a bipolar electrode. Subsequently, the positive electrode 5 and the negative electrode 3 were alternately inserted into the space formed by facing the separator 4. Here, the positive electrode tab 5c of the positive electrode current collector 5a and the negative electrode tab 3c of the negative electrode current collector 3a were projected from the separator 4 in the same direction. 13, the positive electrode tabs 5c and the negative electrode tabs 3c are overlapped with each other in the stacking direction of the negative electrode 3, the separator 4 and the positive electrode 5, and the positive electrode tab 5c And the negative electrode tab 3c are not overlapped.

Subsequently, a plurality of overlapping negative electrode tabs 3c were welded to each other, and they were connected to negative electrode terminals. Similarly, a plurality of overlapping positive electrode tabs 5c are welded to each other, and they are connected to positive electrode terminals.

&Lt; Preparation of non-aqueous electrolyte &

LiPF ₆ was dissolved at a concentration of 1 M in a mixed solvent of propylene carbonate and diethyl carbonate in a volume ratio of 1: 2. Thus, a nonaqueous electrolyte was prepared.

<Fabrication of Battery>

The electrode group 2 thus obtained was housed in a sheathing member of a laminate film. At this time, the negative electrode terminal and the positive electrode terminal were extended to the outside of the sheathing member. Then, the periphery of the laminated film was welded while leaving a part thereof. Next, the previously prepared non-aqueous electrolyte was put into the exterior member through a non-welded portion (injection hole) of the laminated film. Then, the injection holes were welded to produce the nonaqueous electrolyte battery of Example 1 having a capacity of 1.0 Ah.

[exam]

The rate test and the cycle test were carried out for each of the batteries manufactured as described above in the following procedure.

(Rate test)

First, each battery was charged at a rate of 1C until the battery voltage reached 3.0V, and then charged at a constant voltage of 3.0V until the current value reached 0.05C. Then, the battery was discharged at a rate of 0.2C until the battery voltage reached 1.5V. The discharge amount obtained from this discharge was recorded as a 0.2C discharge amount.

Subsequently, each battery was charged at a constant rate until the battery voltage reached 3.0 V at a rate of 1C, and then charged at a constant voltage of 3.0 V until the current value reached 0.05C. Then, the battery was discharged at a rate of 5C until the battery voltage reached 1.5V. The discharge amount obtained by this discharge was recorded as the discharge amount of 5C.

The ratio of the 5C discharge amount of each battery to the 0.2C discharge amount was calculated as a 5C / 0.2C capacity ratio as an index of rate characteristics.

(Cycle test)

After the rate test, each cell was subjected to a cycle test in the following procedure. First, each battery was charged at a rate of 1 C until the battery voltage reached 3.0 V, and then charged at a constant voltage of 3.0 V until the current value reached 0.05 C. Then, the cell was left at a constant temperature of 25 캜. Then, the battery was discharged at a rate of 5C until the battery voltage reached 1.5V. Charge-stop-discharge was set to one cycle. Between cycles, the reaction was allowed to stand for 10 minutes. In the cycle test, the above cycle was performed for 1000 cycles. The cycle test was carried out at a constant temperature of 25 캜.

The ratio of the discharge amount discharged by the 1000th cycle discharge to the discharge amount discharged by the first cycle discharge was calculated as the cycle capacity retention rate as an index of the cycle life characteristic.

[result]

First, synthesis conditions of the active materials in the respective Examples and Comparative Examples are summarized in Table 1 below.

Then, the crystallite size and aspect ratio of the active material contained in the active materials of each of the examples and the comparative examples and the 5C / 0.2C capacity ratio and the cycle capacity retention ratio of the test batteries in each example and each of the comparative examples were measured by the following methods Table 2 summarizes.

[Review]

First, Examples 1 to 18 are all examples in which an active material is synthesized by liquid phase synthesis. On the other hand, Comparative Examples 1 to 3 are examples in which an active material is synthesized by solid phase synthesis. In the solid phase synthesis of Comparative Examples 1 to 3, a long time firing was required. Therefore, as shown in Table 1, the active material particles of Comparative Examples 1 to 3 had a large crystal size and a high aspect ratio of primary particles. Actually, as is apparent from a typical SEM image of the active material of Comparative Example 1 shown in Fig. 12, the active material of Comparative Example 1 contained large active material particles having an increased aspect ratio. On the other hand, in Examples 1 to 18, the heating rate at the time of baking was 20 ° C / min or more. By the synthesis by the liquid phase method, it was possible to suppress the increase of the crystallite size and the aspect ratio of the primary particles even when a compound containing at least one element selected from the group consisting of Mo, V and W was used as the sintering aid . Therefore, the test batteries of Examples 1 to 18 can suppress the increase of the diffusion distance of Li in the active material in the negative electrode, and as a result, the capacity ratio of 5C / 0.2C and the cycle capacity retention ratio are superior to those of Comparative Examples 1 to 3 Which is more improved than those of

Further, in Examples 1 to 4 and Comparative Examples 8 and 9, Mo is used as the additive element, and the content of the additive element in the niobium-titanium composite oxide is changed. From the results shown in Table 2, it was found that the test batteries of Examples 1 to 4, in which the content of Mo in the niobium titanium composite oxide was in the range of 0.01 atom% to 2 atom% It can be seen that the capacity ratio of 5C / 0.2C and the cycle capacity retention ratio are improved as compared with the test battery of Comparative Example 9 in which the content of the test battery and Mo is too small. This is because, in the active materials of Examples 1 to 4, a niobium titanium composite oxide in which a Mo-containing compound was included as a sintering aid at the time of calcination and in which a part of Nb and / or Ti was substituted with Mo element was synthesized, As shown, it is possible to suppress the increase of the crystallite size and the aspect ratio of the primary particles.

On the other hand, in the active material of Comparative Example 8, the content of Mo in the niobium-titanium composite oxide exceeds 2.00 atm%, which is considered to exceed the solubility limit of Mo in the niobium-titanium composite oxide. Therefore, the active material particles of the niobium-titanium composite oxide contained in the active material of Comparative Example 8 were in a state in which much of the active material particles remained in the active material. This is also supported by the results of wide angle X-ray diffraction measurement on the active material of Comparative Example 8. In the active material of Comparative Example 8 including the above-mentioned active material particles, cracking of the active material occurred due to the volume expansion and shrinkage accompanying shrinkage during insertion and extraction of Li, and therefore, the cycle characteristics were considered to be degraded.

In addition, in the active material of Comparative Example 9, the content of Mo in the niobium-titanium composite oxide was less than 0.01 atm%, and the amount of Mo as a sintering aid was considered to be small. Therefore, in the active material of Comparative Example 9, densification did not progress sufficiently during firing, and it was considered that an image having sufficient crystallinity could not be obtained. Therefore, it is considered that the test battery of Comparative Example 9 had a lowered rate characteristic and cycle life characteristic.

It can be seen from the results of Examples 10 to 12 and Comparative Examples 10 and 11 that the same tendency as in Mo is also obtained when W is used as an additive element. Further, from the results of Examples 13 to 15 and Comparative Examples 12 and 13, it can be seen that the same tendency as in Mo also occurs when the addition element is V.

The active material of Comparative Example 14 was synthesized without adding any of Mo, W and V to the starting material. Since the active material of Comparative Example 14 was synthesized without using a raw material to be a sintering aid, the crystallinity was low even though the sintering temperature was 900 캜. Therefore, the test battery of Comparative Example 14 was thought to have a lower capacity and a cycle capacity retention ratio of 5C / 0.2C than the test battery of Example 1, because diffusion of bulk Li in the active material of Comparative Example 14 was inhibited .

In Examples 5 and 6 and Comparative Examples 4 and 5, the firing temperature was changed from Example 1. In Examples 5 and 6, by including a compound containing Mo in the starting material, this compound served as a sintering aid. For this reason, although the active materials of Examples 5 and 6 were synthesized by lowering the firing temperature to 800 ° C. and 700 ° C., respectively, the test batteries of Examples 5 and 6 had a capacity ratio of 5C / 0.2C and a cycle capacity The retention rate did not drop. On the other hand, in Comparative Example 4 in which the firing temperature exceeded 1000 캜, since the crystallite size of the obtained active material particles became too large, the diffusion distance of Li in the active material particles was increased. As a result, It is considered that the characteristics are degraded. On the other hand, the active material of Comparative Example 5 was considered to have a too small crystallite size of the obtained active material particles because the firing temperature was too low. It is considered that the active material of Comparative Example 5 had an excessively small crystallite size of the active material particles, so that the Li intercalation site became unstable due to the influence of the active material interface and further the side reaction increased. Therefore, it is considered that the test battery of Comparative Example 5 lacked the cycle characteristics.

Examples 7 to 9 and Comparative Examples 6 and 7 are examples in which the rate of temperature rise was changed from Example 1. In the active materials of Comparative Examples 6 and 7, since the rate of temperature rise at firing was too low, the aspect ratio of the primary particles of the obtained active material particles exceeded 4. Therefore, it is considered that the diffusion distances of Li in the active material in the negative electrode of the test batteries of Comparative Examples 6 and 7 are increased. As a result, it is considered that the test batteries of Comparative Examples 6 and 7 lacked the cycle characteristics.

According to at least one of the embodiments and examples described above, a battery active material is provided. The battery active material includes active material particles of a monoclinic niobium titanium composite oxide. The monoclinic niobium titanium composite oxide contains at least one kind of element selected from the group consisting of Mo, V and W. The content of at least one element selected from the group consisting of Mo, V and W in the monoclinic niobium titanium composite oxide is in the range of 0.01 atm% to 2 atm%. In the active material particle, the aspect ratio of the primary particles is in the range of 1 to less than 4. The crystallite size of the active material particles is in the range of 5 nm or more and 90 nm or less. This battery active material is capable of suppressing generation of an overvoltage upon charging and a side reaction at the reduction side when used in a built-in nonaqueous electrolyte battery because the diffusion length of the Li solid in the active material particle during crystal growth is suppressed. As a result, the battery active material can realize a nonaqueous electrolyte battery excellent in input / output characteristics and cycle characteristics.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other forms, and various omissions, substitutions, and alterations can be made without departing from the gist of the invention. These embodiments and their modifications fall within the scope and spirit of the invention, and are included in the scope of the invention as defined in the claims and their equivalents.

Claims (15)

And an active material primary particle of a monoclinic niobium titanium composite oxide containing at least one element selected from the group consisting of Mo, V, and W,
The content of the at least one element in the monoclinic niobium titanium composite oxide is in the range of 0.01 atm% to 2 atm%
Wherein the active material primary particles have an aspect ratio in a range of 1 to less than 4 and a crystallite size in a range of 5 nm to 90 nm. The method according to claim 1,
Wherein the active material primary particles have an aspect ratio of 1 or more and 3 or less. 3. The method according to claim 1 or 2,
Wherein the active material primary particles have a crystallite size of 10 nm or more and 70 nm or less. 3. The method according to claim 1 or 2,
Wherein the content of the at least one element in the single crystal niobium titanium composite oxide is 0.01 atm% to 0.3 atm%. 3. The method according to claim 1 or 2,
Wherein the monoclinic niobium titanium composite oxide comprises at least one element selected from the group consisting of Ta, Fe, Bi, Sb, As, P, Cr, B, Na, Mg, . 3. The method according to claim 1 or 2,
The single yarn shaping niobium-titanium composite oxide has the formula: Ti _{1 -a- c} M1 _a M2 _b M3 _c Nb _{2 -bd} M4 _d O represented by _7, active material:
In the above formulas,
0? A <1, 0? B <1, 0 <c + d <1,
M1 and M2 are at least one element selected from the group consisting of Nb, Ta, Fe, Ti, Bi, Sb, As, P, Cr, B, Na, Mg, Al and Si. May be the same or different from each other,
M3 and M4 are at least one kind of element selected from V, Mo and W, and M3 and M4 may be the same or different from each other. 3. The method according to claim 1 or 2,
And a carbon-containing layer coated on at least a part of the surface of the active material primary particle. 3. The method according to claim 1 or 2,
And secondary particles formed by aggregating the active material primary particles. 3. The method according to claim 1 or 2,
And an active material secondary particle of the monoclinic niobium titanium composite oxide. A negative electrode comprising the active material according to claim 1 or 2,
The positive electrode,
Non-aqueous electrolyte
And a nonaqueous electrolyte battery. A battery pack comprising the nonaqueous electrolyte battery according to claim 10. A nonaqueous electrolyte secondary battery comprising a plurality of nonaqueous electrolyte batteries, each of the plurality of nonaqueous electrolyte batteries comprising: a negative electrode comprising the active material according to any one of claims 1 to 3;
The positive electrode,
Non-aqueous electrolyte
And,
Wherein the plurality of non-aqueous electrolyte batteries are electrically connected in series and / or in parallel. A battery pack comprising the assembled battery according to claim 12.
The method according to claim 1,
Wherein the active material primary particles have an aspect ratio of 1.21 or more and less than 4, The method according to claim 1,
Wherein the active material primary particles have an aspect ratio of 1.21 to 3.82.

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